Interstellar comet 3I/ATLAS is up to 12 billion years old and unlike anything found in our solar system, new James Webb Space Telescope (JWST) observations suggest.

Comet 3I/ATLAS became a celestial celebrity last year after the interstellar visitor was discovered hurtling through our cosmic neighborhood. Not long after, online speculation suggested that the space rock could be an alien spacecraft. However, most astronomers are confident that 3I/ATLAS is a comet from an unknown star system.

Now, new preliminary findings from a study posted to the preprint server Research Square, which are still under peer review, suggest the comet formed in a cold and distant region of the Milky Way around 10 billion to 12 billion years ago. That would make comet 3I/ATLAS more than twice as old as Earth (4.5 billion years old) and our solar system (4.6 billion years old), and at its upper range, not far off the ages of our Milky Way galaxy and the universe itself (about 13.6 and 13.8 billion years old).

Researchers already knew from the comet's speed and trajectory that it was potentially the oldest comet ever seen. Previous estimates put the comet's age at somewhere between 3 billion and 11 billion years old. The new findings further narrowed down the comet's age and origin by looking at isotope measurements taken by JWST when the comet flew past Earth in December 2025.

"They show that 3I/ATLAS isotopic composition is very different from solar system comets and suggest that it likely formed 10-12 billion years ago," Romain Maggiolo, a research scientist at the Royal Belgian Institute for Space Aeronomy who was not involved in the study, told Live Science in an email. "In other words, 3I/ATLAS formed in a stellar environment different from ours, not only somewhere else in space, but also at a much earlier time in the history of the Milky Way."

Comet 3I/ATLAS is only the third interstellar object ever recorded in our solar system. The space rock, which Hubble Space Telescope observations suggest is somewhere between 1,400 feet (440 meters) and 3.5 miles (5.6 kilometers) wide, zoomed into our solar system at around 137,000 mph(221,000 km/h) last year before slingshotting around the sun.

After reaching its closest point to our star, known as perihelion, on Oct. 29, 2025, the comet then made its closest approach to Earth on Dec. 19, when it came within about 168 million miles (270 million km) of our planet. JWST made the observations that have been analyzed in the new study a few days later on Dec. 22.

A relic from the ancient universe

Comets heat up as they fly closer to stars, which causes ice on their surfaces to sublimate into gas. By studying the composition of this gas, researchers can start to figure out what they're made of and the conditions in which they formed.

The authors of the new preprint looked at the ratio of isotopes, or versions of elements, in material outgassed by 3I/ATLAS. They found that the comet's water is more enriched in deuterium, a heavier hydrogen isotope, than any previously studied comet, while its ratio of carbon isotopes also exceeded levels normally seen in our solar system.

The results offer clues to what conditions may have been like in whatever ancient planetary systems forged the comet in the early years of the Milky Way.

"If 3I/ATLAS is indeed as old as this study suggests, the large amounts of volatile molecules it contains indicate that rich prebiotic chemistry may already have been occurring in star-forming regions very early in the history of our Galaxy," Maggiolo said.

The results also indicate that the comet formed in a cold environment that was around 30 kelvins (minus 406 degrees Fahrenheit, or minus 243 degrees Celsius), likely in a dense and well-shielded protoplanetary disk, according to the study.

While the study is still in the preprint stage, Maggiolo, who has studied comet 3I/ATLAS as part of his own research, didn't have any major concerns about it. The new measurements help researchers "better understand this interstellar messenger," he said.

Josep Trigo-Rodríguez, the research principal investigator of the Asteroids, Comets and Meteorites research group at the Institute of Space Sciences (CSIC/IEEC) in Spain who has previously identified erupting "ice volcanoes" on comet 3I/ATLAS, described the new findings as a good compilation of scientific results, using different techniques from well-recognized experts.

"This manuscript exemplifies that interstellar comets are unique bodies that are able to sample remote regions of our Milky Way galaxy," Trigo-Rodríguez told Live Science in an email.

There's a good chance that researchers will never know which star system birthed comet 3I/ATLAS. The comet has likely been traveling through space for billions of years and has come a very long way in that time. Maggiolo's own research has found evidence that the object is extremely irradiated, with all that time in space exposing it to cosmic rays that could have fundamentally altered its chemical composition, making its origins more difficult to decipher.

"The isotopic composition of the material outgassed by 3I/ATLAS provides a crucial new piece of the puzzle," Maggiolo said. "But the puzzle is far from being complete!"

Finding those puzzle pieces is a race against time for astronomers, as comet 3I/ATLAS is now hurtling out of the solar system. It's currently passing Jupiter, where it is expected to make its closest approach on Sunday (March 15). The comet will come within about 33 million miles (54 million km) of the gas giant — much closer than it got to Earth.

The interstellar traveller will then continue its journey away from us, crossing Saturn's orbit in July, Uranus' orbit in April 2027 and Neptune's orbit in March 2028. You can track the comet using NASA's Eyes on the Solar System simulation of the comet's trajectory.

The arrival of 3I/ATLAS in our solar system spawned multiple proposals for a rendezvous mission to study it up close. As the third interstellar object (ISO) ever detected, the wealth of information direct studies could provide would be groundbreaking in many respects. However, the mission architecture for intercepting an interstellar comet poses numerous significant challenges for mission designers and planners. Chief among them is the technological readiness level (TRL) of the proposed propulsion systems, ranging from conventional rockets to directed-energy propulsion (DEP).

So far, mission proposals have focused on chemical rockets launched from Earth, like NASA's Janus mission and the ESA's Comet Interceptor, or on existing missions like the Juno probe adjusting their trajectories to rendezvous with it. In a recent paper, researchers from the Initiative for Interstellar Studies (i4is) propose foregoing a direct transfer mission that would launch from Earth today. Instead, they demonstrate how a mission launching in 2035 could intercept 3I/ATLAS using an indirect Solar Oberth maneuver.

Adam Hibberd, a software and research engineer in Astronautics with the i4is and the owner/director of Hibberd Astronautics Ltd., led the study. He was joined by T. Marshall Eubanks, the Chief Scientist at Space Initiatives Inc. and the CEO of Asteroid Initiatives LLC., and Andreas Hein, an Associate Professor of Aerospace Engineering at the University of Luxembourg and the Chief Scientist at the Interdisciplinary Centre for Security, Reliability and Trust. Their paper has accepted for publication in the Journal of the British Interplanetary Society (JBIS).

The main challenges for a direct mission to rendezvous with 3I/ATLAS stem from the target object's celestial mechanics, its high heliocentric speed, and the late initial detection. The first issue effectively rules out a rendezvous mission that relies on an onboard propulsion system to match the comet's velocity, thereby enabling a prolonged close-up study of the body. As a result, a flyby mission is the preferred option. However, the second and third considerations rule out a direct mission because the optimal launch date had already passed before it was detected. As Hibberd summarized these for Universe Today via email:

"For the direct mission, the object 3I/ATLAS was detected too late, when it had already travelled inside the orbit of Jupiter, and with a velocity in excess of 60 km/s. It turns out, this was after the optimal launch date for a direct mission to intercept it. One paper found that there would even have been difficulties for a ‘Comet Interceptor’ spacecraft had it been already loitering at the sun/Earth L2 point when 3I/ATLAS was discovered."

This is where Hibberd employed the Optimum Interplanetary Trajectory Software (OITS), which he designed, to assess the feasibility of direct and indirect missions to intercept ISOs. This software has a proven track record for solving missions with Solar Oberths, which includes a previous i4is study for a mission (Project Lyra) that would intercept the first ISO ever detected, 'Oumuamua. Integral to Project Lyra and other missions utilizes OITS is the use of gravitational assists (GAs) and/or Oberth Maneuvers.

The former involves a slingshot maneuver that leverages a planet's (or moon's) gravity to increase speed. The latter consists of a spacecraft under the gravitational influence of a massive body (the sun), waiting to reach its closest pass (perihelion), then applying thrust to achieve a high heliocentric speed. The spacecraft can either achieve escape velocity from the solar system this way, or pick up enough speed to rendezvous with an ISO that has already traveled a huge distance by this time. Said Hibberd:

"For the direct mission, the object 3I/ATLAS was detected too late, when it had already travelled inside the orbit of Jupiter, and with a velocity in excess of 60 km/s. It turns out, this was after the optimal launch date for a direct mission to intercept it. One paper found that there would even have been difficulties for a 'Comet Interceptor' spacecraft had it been already loitering at the Sun/Earth L2 point when 3I/ATLAS was discovered."

The Solar Oberth option is designed for when an interstellar object has passed through its perihelion (closest approach to the sun) and is receding rapidly away from the sun. It recognizes the fact that a humongous speed needs to be generated by a spacecraft to catch such an object and exploits the so-called ‘Oberth Effect’ in order to generate this speed. When a spacecraft approaches the sun, the sun’s gravitational attraction increases its velocity until the perihelion is reached, then the spacecraft burns its solid-propellant engines at this optimal point, to maximize the ‘slingshot effect’, and to accelerate the probe expeditiously to the target object, in this case 3I/ATLAS.

Based on their OITS simulations, the team found that an intercept could be achieved via a Solar Oberth maneuver, but the launch would have to occur in 2035 to achieve optimal alignment between Earth, Jupiter and 3I/ATLAS. The flight duration would be 50 years (though Hibberd notes that this could be reduced marginally). "2035 is optimal because the alignments of the celestial bodies involved (i.e. the Earth, Jupiter, sun, and 3I/ATLAS) are the most propitious to reach 3I/ATLAS with a minimum Solar Oberth propulsion requirement from the probe, a minimum performance requirement for the launch vehicle, and a minimum flight time to the target," he said.

While such a mission would take a long time to intercept an ISO, the scientific returns would be nothing short of revolutionary. Asteroids and comets are essentially material leftover from the formation of planetary systems. As such, the study of ISOs would reveal things about other star systems without having to send missions to them, which could take centuries or longer. While DEP is being investigated as a possible solution, a la Swarming Proxima Centauri (another i4is project), the TRL of this concept is likely many decades away.

In the meantime, a spacecraft developed with current technology that relies on a Solar Oberth maneuver could reach an ISO and provide a detailed analysis in the same time frame. Even if we never send missions to nearby stars to observe what is there, an ISO interceptor could tell us all we need to know about systems beyond ours.

The original version of this article was published on Universe Today.

A striking "green comet" about the size of a small city is lighting up the night sky as it nears Earth next week. Experts predict the hefty iceball may soon be permanently ejected from the solar system, dooming it to drift through interstellar space — like the "alien" comet 3I/ATLAS.

The new comet, dubbed C/2024 E1 (Wierzchoś), was discovered in March 2024 by Polish astronomer Kacper Wierzchoś, who spotted the icy object sailing toward us with a 4.9-foot (1.5 meter) telescope at the Mount Lemmon Observatory in Arizona. The comet has since been observed by the James Webb Space Telescope (JWST), which detected large amounts of carbon dioxide in its coma — the cloud of gas and dust that surrounds the comet's icy shell.

An initial analysis of JWST data suggested that Comet Wierzchoś' nucleus has a diameter of around 8.5 miles (13.7 kilometers), which is roughly two-thirds the length of Manhattan and around four times the island's width. However, a more recent study, which has not yet been peer-reviewed, hints that this may be an overestimate.

Comet Wierzchoś originates from the Oort cloud — the expansive reservoir of comets and other icy objects lurking near the outer edge of the solar system — and is hyperbolic, meaning that it has an open and flattened trajectory, and does not repeatedly orbit the sun. This is likely the first time it has ever ventured into the inner solar system, the researchers suspect.

Some researchers believe that it has been slowly falling toward the sun for between 1 million and 3 million years, although it is hard to tell for sure. But most experts agree that the gravitational kick from its current solar slingshot will fire it out of our cosmic neighborhood forever and into interstellar space, according to Spaceweather.com.

The eccentric iceball recently passed its closest point to our home star, known as perihelion, on Jan. 20, reaching a minimum distance of around 52 million miles (84 million km) from the solar surface, Live Science's sister site Space.com previously reported.

It will soon make its closest approach to Earth, on Tuesday (Feb. 17), when it will be around 94 million miles (151 million km) from our planet — roughly the same distance away as the sun.

Going, going, gone

According to the researchers, it could take several decades or even centuries for Comet Wierzchoś to officially leave the solar system. But once it has, it will spend millions if not billions of years drifting through the Milky Way, sporadically passing through other alien star systems on its way.

This is exactly what happened to the interstellar comet 3I/ATLAS, which made headlines last year as it shot through the inner solar system, having been kicked out by its home star likely long before the sun was born.

3I/ATLAS was first spotted in July and reached perihelion in late October, before swinging past Earth in mid-December. During this period, it displayed many unusual characteristics, which led some scientists to controversially propose that it may be an alien spacecraft — despite overwhelming evidence that it is a natural comet.

It is now on its way back out of the solar system and will likely pass through many other star systems, much like Comet Wierzchoś eventually will.

How to see C/2024 E1 (Wierzchoś)

Since Comet Wierzchoś passed perihelion, it has become significantly brighter and grown a long tail of gas and dust, allowing astrophotographers to snap spectacular shots of it speeding across the night sky. Austrian astrophotographer Gerald Rhemann captured one of the best photos of the iceball on Jan. 26 from a night sky reserve in Namibia (see above).

Many of these photos, including Rhemann's, show the comet's coma glowing green. This rare hue is likely tied to its high carbon content, as seen in previous comets, although the exact cause of its coloration has not been reported on by researchers.

The emerald iceball will not become bright enough to be visible to the naked eye. However, it can be easily spotted with a decent telescope or pair of stargazing binoculars.

From the Northern Hemisphere, it will remain observable over the next few weeks and can be best spotted above the southwestern horizon after sunset, as it passes through the constellation Sculptor, according to EarthSky.com. However, it will be easier to spot from the Southern Hemisphere.

For more information on exactly when and how to see the comet for yourself, you can visit TheSkyLive.com.

Close encounters of the cometary kind

2026 is shaping up to be another bumper year for comet enthusiasts, following on from the excitement of 3I/ATLAS, as well as other comets like Lemmon and SWAN, last year.

In recent weeks, astronomers have spotted a new "sungrazer" comet, dubbed C/2026 A1 (MAPS), which could potentially become bright enough to be seen with the naked eye during the daytime in early April — if it survives its extremely close slingshot around the sun.

Another hefty iceball, dubbed C/2025 R3 (PanSTARRS), could also become visible without a telescope as it nears its closest points to both the sun and Earth in late April.

With the help of the newly operational Vera C. Rubin Observatory, some researchers are also hoping that we may soon find many more hidden objects — potentially including the solar system's next interstellar visitor.

The final frontier is an unendingly beautiful expanse filled with unimaginable wonders, making it the perfect sandbox for photographers, astronomical observatories and space-based telescopes to capture incredible images that we can hardly fathom. And 2025 was no different.

This year, we covered a range of stunning space images, from an eye-catching alien comet and a planetary parade portrait to the first Vera C. Rubin photos and otherworldly animal lookalikes. Here are 10 of our absolute favorites.

Alien visitor transforms into a "cosmic rainbow"

The biggest space news story this year was undoubtedly the arrival of the third-ever interstellar object 3I/ATLAS, which has dominated headlines and astronomers' attention ever since it was first spotted speeding through the solar system in early July. As a result, there has been no shortage of stunning shots of the alien comet.

Our favorite is this timelapse image captured by the Gemini North telescope on the summit of Hawaii's Mauna Kea volcano. The image was created by combining 16 different photos using multiple colored filters to create a giant cosmic rainbow.

Read more: Interstellar comet 3I/ATLAS transforms into a giant 'cosmic rainbow' in trippy new telescope image

"The Fall of Icarus"

One of the most unbelievable photos of 2025 was this solar spectacle, dubbed The Fall of Icarus, which perfectly captured the moment a skydiver fell directly in front of the sun.

Astrophotographer Andrew McCarthy captured this shot in early November, at a distance of around 8,000 feet (2,440 meters) from the skydiver, YouTuber Gabriel C. Brown. It took six attempts to properly line up Brown with the solar surface before the thrill-seeker leapt from a small propeller-powered craft at an altitude of around 3,500 feet (1,070 m).

"It was a narrow field of view, so it took several attempts to line up the shot," McCarthy told Live Science. "Capturing the sun is something I'm quite familiar with, but this added new challenges."

Read more: Astrophotographer snaps 'absolutely preposterous' photo of skydiver 'falling' past the sun's surface

Vera C. Rubin's stream of stars

In June, the most powerful digital camera on Earth winked on. The Vera C. Rubin Observatory in Chile's Atacama desert revealed its first-ever images in June. These debut photos were chock-full of cosmic treasures, including the spiral galaxy M61 (shown here), which researchers noticed was being trailed by a massive stellar tail around the same size as the Milky Way.

We can look forward to many more spellbinding shots from Rubin in the coming years as it begins its decade-long survey of the night sky.

Read more: First Vera Rubin Observatory image reveals hidden structure as long as the Milky Way trailing behind a nearby galaxy

Perfect planetary parade portrait

In late January and early February, up to six of the solar system's planets were simultaneously visible in the night sky in what astronomers refer to as a "planetary parade." This particular parade was one of the best in recent years, allowing astrophotographers to snap several stunning pics of the event.

Our favorite pick of the bunch is this planetary portrait from French astrophotographer Gwenaël Blanck, which he digitally edited to show each planet alongside the sun in the order of distance from Earth. Blanck snapped each of the individual worlds within 80 minutes of one another.

Read more: Parisian photographer produces phenomenal, perfectly-proportioned 'planetary parade' portrait

Giant "diamond ring" shines in X-ray

All that glitters is not gold, and in this scintillating starscape, released in November, it is high-energy X-rays that sparkle like a giant ring.

This object, dubbed a "diamond ring," is an expanding bubble of gas in a star-forming region of the Cygnus constellation. The glowing bubble is around 20 light-years across and is around 400,000 years old. It was photographed by NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA), which previously scanned the night sky from a telescope onboard a Boeing 747SP aircraft, at an altitude of more than 45,000 feet (13,700 m).

The cosmic ring is not to be confused with Einstein rings, which are rings of light created by gravitational lensing.

Read more: Giant 'diamond ring' sparkles 4,500 light-years away in the Cygnus constellation

A cosmic butterfly spreads its wings

JWST has, yet again, captured some stunning photos in 2025, including the fiery Cigar Galaxy, a tantruming stellar toddler and a "starlit mountaintop" nebula. However, our favorite is this striking portrait of the "Butterfly Star," IRAS 04302+2247.

The insect imposter's shining wings are made from a mini nebula of stellar material leftover from a supernova. This nebula is bisected by a protoplanetary disk that surrounds the baby star like a cosmic cocoon, and just happens to be aligned with Earth so that the two halves of the nebula are seen from side-on. It is located around 525 light-years away, in a star-forming region, known as the Taurus Molecular Cloud.

Read more: James Webb telescope finds a warped 'Butterfly Star' shedding its chrysalis

Arsia Mons rises

Speaking of Mars, NASA's Mars Odyssey orbiter also captured this stunning shot of a giant dead volcano peeking above the clouds on the Red Planet, as eerie green lights dance above the Martian horizon.

The mountain in the image is Arsia Mons, which stands at more than 12 miles (19 kilometers) above the surface of the previously volcanic Tharsis plateau. The extinct volcano is more than twice as tall as Mount Everest, but around 4 miles (6 km) shorter than Mars' tallest peak, Olympus Mons.

The green lights look like auroras. But they are actually just an effect of the image being partially captured using infrared light, which emanates from the planet's wispy atmosphere.

Read more: NASA spots Martian volcano twice the height of Mount Everest bursting through the morning clouds

Seen by the "Eye of Sauron"

There is no escaping the dark lord of Mordor's malevolent gaze, even from halfway across the universe. That's the impression given by this photo, dubbed the "Eye of Sauron," which playfully references J. R. R. Tolkien's fantasy epic "The Lord of the Rings."

The "eye" is actually the magnetic field of a supercharged energy jet being shot into space by a quasar — a supermassive black hole at the center of a distant galaxy. This quasar, dubbed PKS 1424+240, is billions of light-years from Earth and has one of its jets pointed almost directly at our planet, allowing researchers to peer directly through its "jet cone" and map out the magnetic swirls within.

Read more: Giant, cosmic 'Eye of Sauron' snapped staring directly at us in stunning 15-year time-lapse photo

New "heavenly" pillars emerge

This ethereal image shows a set of stellar structures reminiscent of the famous "Pillars of Creation," first seen by the Hubble Space Telescope in 1995. The structure is named Ua 'Ōhi'a Lani, which means the "heavenly rains" in Hawaiin, and this image of it was taken by the Gemini North telescope.

What you are seeing is two distinct regions: the twinkling blue stars of a star cluster, named NGC 6823, overlapping the veil of red gas that comprises a more distant emission nebula, dubbed NGC 6820. The ethereal pillars are made from additional gas and dust that have been sculpted by the foreground stars' intense radiation.

The original pillars of creation were also recently given a glow-up by JWST, which captured the iconic cosmic structures using infrared light.

Read more: 'Heavenly rains': Ethereal structure in the sky rivals 'Pillars of Creation'

Astronaut snaps a giant "jellyfish" over Earth

As incredible as it is to point our cameras out into the universe, space also provides a unique angle of our own planet. And that's exactly the case in our final photo, which shows off a giant, electrifying "jellyfish" hovering above Earth.

The luminous branching structure was snapped by NASA astronaut Nichole Ayers in July, while onboard the ISS. It shows a type of transient luminous event that researchers commonly call sprites. In this case, the red jellyfish-like sprite formed at the summit of a rare upward-shooting "gigantic jet" of lightning, up to 50 miles (80 km) above the U.S.-Mexico border.

If you liked this photo, then be sure to check out Live Science's weekly Earth from space series for more incredible images of our planet from above.

Read more: Astronaut snaps giant red 'jellyfish' sprite over North America during upward-shooting lightning event

Want to see more amazing images of the cosmos?Be sure to check out Live Science's Space Photo of the Week series, or peep our favorite space shots from 2024 or this gallery of stunning James Webb Space Telescope (JWST) images.

We've watched it speed through the solar system using the most powerful telescopes in human history. We've studied its light with probes whipping around the sun and robots marooned on Mars. Countless eyes watched it make its closest approach to Earth on Dec. 19 — and yet, for all of this, the interstellar comet 3I/ATLAS remains little more than a blur of gas, shrouded in mystery.

Since its discovery in early July, 3I/ATLAS has been studied more enthusiastically than practically any other celestial object in recent memory. Still, for all its fame, much remains unknown about it. The comet’s origins, from somewhere far across our galaxy, may never be known. Its true age, size, composition, and shape are also poorly constrained.

But how can we learn more about this alien interloper — or indeed, the next one — when we’re already studying it with everything we’ve got?

Some scientists are proposing a bold solution: We have to "intercept" it with a spacecraft.

Doing so would not only help us to better understand its key characteristics but also photograph its surface and potentially collect our first-ever interstellar samples, which could help reveal how alien exoplanets form, how common our type of solar system is and maybe even help answer the question of whether or not we are alone in the universe.

"We only have one shot at this object and then it's gone forever," Darryl Seligman, an astronomer at Michigan State University and the lead author of the first paper published about 3I/ATLAS, previously told Live Science. "So we want as much information from all of our observatories as we can possibly get."

Alien interlopers

On July 1, astronomers at the Asteroid Terrestrial-impact Last Alert System (ATLAS) revealed they had spotted a mysterious object traveling toward us from beyond Jupiter, at more than 130,000 mph (210,000 km/h). ATLAS, which automatically scans the skies using telescopes in Hawaii, Chile and South Africa, was hunting for potential threats to Earth. It found something else entirely.

Less than 24 hours later, NASA confirmed that the speeding blur of light was an interstellar object — an alien asteroid or comet that originated outside the solar system — and named it 3I/ATLAS. It was only the third-ever detection of an interstellar object in our solar system, after the anomalous space rock 'Oumuamua in 2017 and Comet 2I/Borisov in 2019.

Despite the rapid spread of unfounded theories that the object could be an alien probe, early observations confirmed that 3I/ATLAS is a comet — potentially the oldest of its kind ever seen — that likely originated from the Milky Way's "frontier" region.

Interstellar visitors like this are exciting to astronomers because they are one of the few opportunities we have to explore neighboring star systems, which would take generations and the invention of sci-fi technology to reach aboard a spacecraft.

"ISOs are relics from planetary formation, so studying these objects and comparing them to what we have closer to us [could] lead to an interesting view of how other planetary systems in the galaxy formed," Pedro Bernardinelli, a planetary scientist at the University of Washington's DiRAC Institute, told Live Science in an email.

But our Earth-based observatories, and even orbiting spacecraft such as the James Webb Space Telescope (JWST), can only tell us very rough information like general size, shape and composition. To really reveal ISO secrets, we will need to get much, much closer — possibly even close enough to grab a fragment.

Doing so won't be easy, but given the valuable insights it could reveal about the star systems beyond our own, it would be well worth the effort, experts say.

"Each one of these ISOs is a little piece of low-hanging fruit from a tree that can tell us a great deal about the trees growing in some other neighborhood," Wesley Fraser, an astronomer with the National Research Council Canada, previously told Live Science.

Giving chase

But the time to catch this speeding comet is fast approaching. 3I/ATLAS is now reaching its closest point to Earth, around 168 million miles (270 million km) miles away. From there it will move quickly away from us and will likely be beyond Neptune within another year.

Because it is now too late to intercept 3I/ATLAS within the inner solar system, most researchers agree that there is now only one viable option to study this object: to chase it down as it leaves the solar system.

This would require the spacecraft to carry out what researchers call "Oberth maneuvers," where a probe is gravitationally slingshotted around massive objects, such as the sun, to pick up enough speed to allow it to catch up to and intercept an ISO at a specific point along its predicted trajectory.

This idea was first proposed in 2022 to catch up with the first known interstellar object, 'Oumuamua. The plan, dubbed Project Lyra, was to launch a probe in 2028 that would intercept and investigate that object, after completing an Oberth maneuver around Jupiter.

But this chaser method has a huge limitation: Scientists would need to wait decades for data to come back. For example, if Project Lyra launched a spacecraft in 2030, it would not intercept 'Oumuamua until 2052 at the earliest, Adam Hibberd, a researcher with the U.K.-based nonprofit Initiative for Interstellar Studies (I4IS) who worked on Project Lyra, told Live Science.

So far, Project Lyra has not moved past the planning stage — making a 2028 launch highly unlikely — but the project could still reach 'Oumuamua if launched in 2030 or 2033, Hibberd said. This means we would likely still have plenty of time to chase down 3I/ATLAS, if we want to.

Future propulsion methods, such as a solar sail, could drastically cut the travel time of missions like this from decades down to just a few years, he added. But these technologies are decades away from becoming a reality themselves.

Playing "hide-and-seek"

But given that 3I/ATLAS will be very hard to chase down, some astronomers argue that we shouldn't bother hunting it. Rather we should prepare to intercept the next interesting ISO.

By launching an interceptor spacecraft and parking it in a gravitationally stable position around Earth, known as a Lagrange point, we could, in theory, be ready to quickly intercept a passing object, they argue.

This idea, also first proposed in 2022, has been dubbed the "hide-and-seek" approach. However, unlike Project Lyra, it is much closer to becoming a reality.

The European Space Agency (ESA) is preparing the Comet Interceptor mission, which is currently scheduled to launch in 2029, on board the same rocket as ESA's Ariel space telescope, said Colin Snodgrass, an astronomer at the University of Edinburgh in Scotland who specializes in comets and was the deputy project investigator on the proposal for this mission.

The Comet Interceptor probe isn't specifically aimed at interstellar visitors. Instead, it's designed to hunt nonperiodic comets like Comet Lemmon, which has been visible in the night sky, alongside 3I/ATLAS, in recent months. These comets drift toward the sun every few hundred or thousand years and have poorly defined orbital pathways around the sun.

When ESA researchers spot a comet they can reach, they will "fire the rockets, get to the right place in space to cross the path of the comet and have this fast flyby encounter, where we go shooting past the comet, getting as much data as we can," Snodgrass told Live Science.

And while the mission is not designed to study interstellar objects, the project will be perfectly placed to intercept them.

"The whole science team is very much in agreement that if an interstellar object was to pop up, we wouldn't let that opportunity go by," Snodgrass said.

The main advantage of the hide-and-seek approach is that we wouldn't have to wait decades for a probe to catch up to its target. Additionally, we'd be reaching it at the best time to study it. That's because interstellar comets, like 3I/ATLAS, soak up more solar radiation when in the inner solar system — which, in turn, means they give off more light, gas and dust, giving us a better chance to learn about their composition.

However, a hide-and-seek mission might not be able to catch all the objects we care about. For example, ESA's Comet Interceptor probe would have been unlikely to reach 3I/ATLAS, had it been in orbit when the ISO was first discovered, because the comet was too far away from us, a recent study from Snodgrass and others found.

Collision course

A major limitation of both the chaser and hide-and-seek missions is that ISOs travel too fast for their respective spacecraft to travel alongside, or rendezvous with, these objects.

This makes it "almost impossible" for the probes to directly obtain samples from the objects' surfaces as NASA did during its OSIRIS-REx mission, which successfully landed a probe on the asteroid Bennu in 2020 and collected samples that were later returned to Earth, Hibberd said. Due to fuel limitations, it is also unlikely that these samples could be easily returned to Earth, especially during a chaser mission, he added.

However, there is a third option that could yield valuable interstellar samples: the "impactor" method.

Similar to NASA's Double Asteroid Redirection Test (DART) mission, which successfully deflected the asteroid Dimorphos after smashing into the space rock in 2022, an interceptor probe could also be sent to crash into an ISO, Hibberd suggested. While this probe would be destroyed, a second spacecraft could be deployed to analyze the debris field and potentially even collect leftover fragments of the alien object, he added.

But an impactor mission would need to overcome serious technical challenges. First, ISOs travel much faster than solar system objects, like Dimorphos, meaning it's more difficult to smash them apart. Second, this method would likely work only on an asteroid, not on comets, which have hard, icy shells. And third, a collision could accidentally send chunks of debris on a collision course with Earth, like DART did. As a result, most of the experts who talked to Live Science, including Hibberd, agreed that it is probably too risky to attempt an impactor mission until more research has been done on the subject.

The perfect mission

If money were no object, we could pursue all of these options. But if an agency like NASA has the budget for only one such mission, which one should be selected?

A chaser mission would allow astronomers to target a specific object they know they want to study, while a hide-and-seek mission would be limited to objects that happened to pass nearby. On the other hand, the hide-and-seek mission could reliably predict objects' locations in the inner solar system, whereas the chaser method would target objects in the dark, more chaotic outer solar system, where it would be harder to find and photograph them, Snodgrass said.

Another issue is that signals from a more distant chaser mission would take longer to send and receive, so mission operators would be unable to monitor and adjust an ISO flyby in real time or fix technical difficulties easily — a difficulty NASA faces with its distant Voyager probes, Snodgrass said.

There is also the matter of money. Project Lyra would likely cost the same as NASA's New Horizons mission, which flew by Pluto in 2015 and cost at least $700 million, Hibberd said. Meanwhile, ESA's Comet Interceptor mission has a budget of around $150 million, Snodgrass said.

As a result, most researchers who spoke to Live Science agreed that a hide-and-seek interceptor would likely be the best way of studying an ISO up close.

But if this is the method we end up using, how should we design the resulting spacecraft to maximize its chances of collecting useful data?

While ESA's Comet Interceptor is relatively inexpensive, a dedicated ISO interceptor mission — with a bigger budget — would allow us to launch a faster probe that could carry more fuel and thus travel farther. However, the craft doesn't need to be fancy.

A "fairly stripped-back" probe with a decent camera and a few spectrographs, capable of analyzing the light given off by the different gases, would be more than enough to collect sufficient data from any flyby, Snodgrass said.

If the probe were intercepting a comet, and not an asteroid, it could also be fitted with a device to catch specks of dust from the comet's coma or tail during a superclose approach, just as NASA's Stardust probe did with "Comet Wild 2" in 2004.

Assuming that the interceptor hasn't depleted its fuel reserves and can be returned to Earth, this may be the only reliable way of actually getting our hands on interstellar samples, Snodgrass said.

To intercept or not to intercept

Once the "perfect" interceptor is in position around Earth, researchers will have to choose which ISO to go after. And because any spacecraft is unlikely to be reusable, it may get only one shot at picking the right target.

We may soon be spoiled for choice. ISOs may be far more common than we realize. "There are likely thousands of other ISOs in the solar system right now," Fraser said. "We just can't see them because they are too faint, too far and too fast."

But thanks to the newly operational Vera C. Rubin Observatory in Chile, which is designed to spot more small and dim objects in the outer solar system, we are likely to find many more ISOs in the coming decades and, more importantly, spot them much earlier on their journey toward us, which would give us a better chance of studying them.

The first thing to consider is whether to go after an asteroid or a comet. Because comets become more active near the sun and present the most likely route for collecting interstellar samples, they would likely take priority, Snodgrass said.

The next consideration would be the target's distance from Earth. As we have already seen, ESA's Comet Interceptor may have struggled to reach 3I/ATLAS on its journey through the inner solar system. Therefore, it might pay to wait for an ISO that is on a favorable trajectory relative to Earth.

Comet 3I/ATLAS whizzed past Earth last night as astronomers worldwide continue to gather data on the interstellar visitor.

The comet made its closest approach at around 1 a.m. EST on Friday (Dec. 19), coming within about 168 million miles (270 million kilometers) of our planet.

When you consider the vastness of space, 168 million miles is a relatively short distance, but even at the comet's nearest point to us, 3I/ATLAS was still almost twice as far away as the sun.

Comet 3I/ATLAS is up to a few miles wide and didn't get close enough to be visible to the naked eye. However, skywatchers observed it using telescopes.

And last night was far from our last chance to see the comet. It will remain observable in the pre-dawn sky with a small telescope until spring, according to NASA. If you don't have a telescope, then the best way to see comet 3I/ATLAS is online.

The Virtual Telescope Project in Italy is hosting a livestream of the comet passing Earth at 11 p.m. EST on Friday. The livestream, which was scheduled for last night but postponed due to rain, will feature real-time images of the comet as it zooms toward Jupiter.

Comet 3I/ATLAS is worth checking out because it's a rare example of an interstellar object from outside of our solar system. This is only the third interstellar visitor ever detected and could be the oldest comet ever seen.

The comet's origins have been the subject of considerable speculation, most notoriously the repeated suggestions that it could be an alien spacecraft. However, nearly all astronomers are confident that 3I/ATLAS is a comet from another star system.

Researchers discovered comet 3I/ATLAS in July, when they spotted an unknown object racing along at around 137,000 mph (221,000 km/h) within the orbit of Jupiter. Having swung past the sun, reaching the closest point to our star (perihelion) at the end of October, the comet is now making its way out of our solar system.

What's next for comet 3I/ATLAS?

Comet 3I/ATLAS will pass Jupiter next, where it is expected to make its closest approach on March 15, 2026, according to NASA. The comet will get much closer to Jupiter than it did to Earth, coming within about 33 million miles (54 million km) of the gas giant. Spacecraft stationed at Jupiter, like Juno, might be able to observe the comet as it approaches.

The interstellar interloper will then cross Saturn's orbit in July 2026; Uranus' orbit in April 2027; and Neptune's orbit in March 2028. However, it won't get close to any of these planets. You can track comet 3I/ATLAS for yourself using NASA's Eyes on the Solar System simulation of the comet's trajectory.

Researchers will keep an eye on comet 3I/ATLAS while it remains in our cosmic neighborhood. After all, there's a lot they still don't know about its properties. For example, the size of the comet is uncertain. Hubble Space Telescope observations suggest that it's somewhere between 1,440 feet (440 meters) and 3.5 miles (5.6 km) wide.

Researchers also don't know which star system forged comet 3I/ATLAS, and they may never find out. The comet travelled a very long way and could have been hurtling through space for billions of years before visiting our solar system.

Editor's note, Dec. 19 at 10:00 a.m. ET: Comet 3I/ATLAS officially passed its closest point to Earth last night and is zooming away from us for good. However, due to rainy conditions in Italy, the Virtual Telescope Project live stream was postponed until 11 p.m. EST on Friday, Dec. 19 (0400 GMT on Dec. 20). Try to catch the free webcast here tonight. You can still see the comet through a decent backyard telescope, as well.

Comet 3I/ATLAS, the third interstellar object ever detected by astronomers, will make its closest approach to Earth overnight between Thursday and Friday (Dec. 18 to 19), when it gets to just 168 million miles (270 million kilometers) from our planet. It poses no threat to Earth.

The precise moment will come at 1 a.m. EST (0600 GMT) on Dec. 19, according to Space.com. Though still just under twice the distance from Earth as the sun — something that will preclude stunning photos from giant telescopes — it’s a unique opportunity to glimpse an object from another star system. Discovered in July 2025, it comes in the wake of 1I/'Oumuamua in 2017 and 2I/Borisov in 2019.

Comet 3I/ATLAS is now on its way away from the sun and out of the solar system, and by far the easiest way to see it before it departs will be online. Using its large telescopes in Manciano, Italy, the Virtual Telescope Project will host a free webcast on YouTube beginning at 11 p.m. EST on Dec. 18 (0400 GMT on Dec. 19). The webcast will also be available as a replay after the live event ends.

Another way to see comet 3I/ATLAS is with a GoTo or smart telescope. Any optical device with a motor can be trained on the object in the constellation Leo. The easiest method is via a smart telescope, such as the Seestar S50, Unistellar eVscope 2, Vaonis Vespera Pro or Celestron Origin; you should be able to find 3I/ATLAS in the app used to control any of these telescopes.

Any planetarium app — such as Sky Tonight, Sky Guide, Stellarium and SkySafari 7 Pro — will also have 3I/ATLAS in its database. That will be helpful to find it visually. Technically, it is visible in large astronomy binoculars, but at magnitude 11, it’s going to look “like a tiny, slightly out-of-focus star,” according to Sky at Night.

A better way to view the comet is with a medium-to-large telescope of about 12 inches, according to NASA, through which observers may spot a faint, fuzzy patch of greenish light close to the bright star Regulus in Leo and a fainter companion, called Rho Leonis.

In the meantime, astronomical telescopes on Earth and in space will continue to monitor it — some from much closer distances than we’ll get. Just today, NASA released new ultraviolet images of the comet taken with its Europa Clipper spacecraft from roughly 102 million miles (164 million km) away, closing the distance from Earth by about a third. Stay tuned for more NASA image releases after the close approach.

A NASA spacecraft designed to hunt for signs of extraterrestrial life has turned its lens toward comet 3I/ATLAS — but not for the reason you might think. The spacecraft just happened to be in the right place at the right time.

Zooming through the solar system at an estimated 153,000 mph (246,000 km/h), the beguiling interstellar comet will reach its closest point to Earth overnight tonight (Dec. 18-19). At its closest, 3I/ATLAS will swoop within about 168 million miles (270 million kilometers) of our planet.

It's close enough that amateur astronomers can spot it with a good backyard telescope, though skywatchers should temper their expectations of seeing much more than a speedy green dot. (See astrophotographer Andrew McCarthey's latest image for a preview.)

Meanwhile, the latest image from NASA — taken with the Europa Clipper spacecraft — cuts the distance to 3I/ATLAS by a third. Snapped on Nov. 6 from a distance of about 102 million miles (164 million km), the new image is the result of seven hours of observations with the craft's Europa Ultraviolet Spectrograph (Europa-UVS) instrument.

Seeing the unseen

Human eyes can't see UV light. But by splitting the observations into their constituent wavelengths and stacking them together, NASA scientists offer a hint of what 3I/ATLAS would look like beyond the visible spectrum. (See also the James Webb telescope's infrared observations and XMM-Newton's X-ray view.)

Clipper happened to be in a prime spot to observe 3I/ATLAS as both objects zoom toward Jupiter; the swift interstellar comet makes its closest approach to the gas giant in March 2026, while Clipper isn't due to arrive there until April 2030.

When it does reach the Jovian neighborhood, Clipper will begin its mission to hunt for signs of extraterrestrial life. The spacecraft's UV instruments will analyze the surface and atmosphere of Europa — one of Jupiter's giant, ice-encrusted moons — and look for geysers carrying chemical clues to the moon's interior. NASA models hint that a liquid water ocean lurks beneath the Europa's crust, which could contain alien life.

An evolving mystery

But the Clipper isn't looking for aliens in this case. (And there's no evidence that 3I/ATLAS is anything other than a natural comet.)

Using the same technology that will ultimately plumb the secrets of Jupiter's moon, Clipper's observations of 3I/ATLAS will be key in analyzing the elements spewing out of the comet and forming the makeshift atmosphere, or coma, around it.

There's no spectroscopic data from Clipper's new UV image yet, but NASA will share its findings as soon as they're available. We do know from prior observations that 3I/ATLAS is rich in carbon dioxide ice, and is releasing diatomic carbon (C₂) gas that gives it the greenish glow seen in recent optical light images.

Until more information rolls in, enjoy this rare close-up view of our solar system's most famous visitor from abroad.

As the interstellar comet 3I/ATLAS prepares for its closest approach to Earth on Dec. 19, it's being monitored not just by space agencies but also the United Nations.

The comet, which will come within roughly 167 million miles (270 million kilometers) of our planet, will be tracked by telescopes around the world so astronomers can pinpoint its location and make predictions about future objects like it.

The U.N.'s International Asteroid Warning Network (IAWN) is about halfway through its 3I/ATLAS observing campaign and expects to publish its findings in a peer-reviewed journal next year, James Bauer, a small-bodies node principal investigator at IAWN and a research professor in the University of Maryland's astronomy department, told Live Science. The network consists of more than 80 observatories and citizen scientists around the world doing active research on near-Earth objects, such as comets and asteroids.

NASA coordinates the IAWN and the network's observing campaigns, Bauer said, and 3I/ATLAS is the first interstellar object to be tracked since the campaigns began in 2017. (Notably, the potentially hazardous near-Earth asteroid Apophis was observed by IAWN in 2020 and 2021, and a new campaign is expected between 2027 and 2029 as the asteroid makes a safe-but-close approach to Earth.)

"The idea behind these campaigns is really to strengthen the technical capabilities for measuring sky positions, which we call astrometry, for asteroids and comets," Bauer said of IAWN's work. The investigators will be testing a new astrometry technique to track the pathway for 3I/ATLAS, which can be helpful for determining how to send a spacecraft to a similar comet in the future.

"We want the community to use the latest and greatest techniques," Bauer said. (Bauer also serves as principal investigator for the NASA Planetary Data System's small bodies node, which archives, catalogs and distributes scientific data related to comets, asteroids and interplanetary dust.)

Tracking 'a comet's comet'

IAWN had been planning an observing campaign like this since October 2024, so 3I/ATLAS was a late-but-fortuitous arrival when it was first spotted in late June. The interstellar comet's upcoming close approach coincides well with the team's planned observing schedule, and because 3I/ATLAS was visible in the network's observatories and of high interest, it seemed like a great fit, Bauer said.

There are challenges in accurately measuring a comet's position, he noted, such as the changing brightness and the variability in its coma, the cloud of gas and dust that extends around the comet’s nucleus and tail as it draws closer to the sun and heats up. These features can inflate the comet’s apparent size and make its location harder to pinpoint.

Luckily, although 3I/ATLAS originated outside the solar system, it's showing such classic comet behavior that it is almost a "comet's comet," Bauer said. For example, it includes components like water and carbon dioxide that are behaving similarly to normal solar system comets.

Community interest has been high. Citizen scientists, observatories large and small, and scientific organizations formed a record 171 campaign participants at the kickoff of IAWN's 3I/ATLAS campaign meeting in October. The mid-campaign teleconference, held Dec. 9 and days before Bauer's interview with Live Science, had 100 campaign participants.

"We've been answering questions from the community — for example, 'How to use the tool? What is the proper format for observing, or for reporting the observations?'" Bauer said.

He said he's grateful for the community's time and interest, as it is helping astronomers refine their ability to report the positions of objects in the sky — including "vigilance" for other near-Earth asteroids and objects that come much closer to our planet.

New telescope images of the interstellar comet 3I/ATLAS confirm that the mysterious object has gotten brighter and greener since its close approach to the sun in late October. This increase in activity could portend new, bright outbursts of cometary material as 3I/ATLAS careens toward its closest encounter with Earth next week.

Taken on Nov. 26 with the Gemini North telescope atop Hawaii's dormant Mauna Kea volcano, the new images capture the comet in one of its most active phases yet. Recently heated by intense solar radiation, ice on the comet is sublimating and spewing into space along with tons of dust, forming a bright, cloudy atmosphere (a coma) around the comet's main body and a long, glowing tail behind it.

To capture this view, the team observed 3I/ATLAS using four filters (blue, red, orange and green), and found that gas in the comet's coma now emits a faint greenish hue, which wasn't the case several months ago.

Why is 3I/ATLAS going green?

Don't rush to blame little green men for the comet's new greenish glow. Among the gases spilling out of 3I/ATLAS is diatomic carbon (C₂) — a molecule of two carbon atoms that emits a greenish light, according to a statement from the National Science Foundation's NOIRLab, which operates the Gemini North telescope along with its twin Gemini South telescope in Chile.

Many solar system comets give off a similar green hue when activated by the sun, including last year's "Mother of Dragons" comet 12P/Pons-Brooks and the recently discovered Comet C/2025 F2 (SWAN).

However, it's noteworthy that 3I/ATLAS appeared distinctly redder when it was first observed by Gemini South in late August, months before its close flyby of the sun, according to NOIRLab. This is evidence that 3I/ATLAS is releasing new molecules into space as it heats up, offering fresh hints into its mysterious makeup.

Is another outburst coming?

As the comet approaches its closest point to Earth on Dec. 19 (coming within a comfortable 170 million miles, or 270 million kilometers, of our planet), we may be in for even more surprises.

"What remains unknown is how the comet will behave as it leaves the Sun's vicinity and cools down," NOIRLab representatives wrote in the statement. "Many comets have a delayed reaction in experiencing the Sun's heat due to the lag in time that it takes for heat to make its way through the interior of the comet. A delay can activate the evaporation of new chemicals or trigger a comet outburst."

3I/ATLAS is the third interstellar object ever discovered, after 1I/'Oumuamua and 2I/Borisov. The comet was detected in late June as it was speeding through our solar system at an estimated 130,000 mph (210,000 km/h), zooming by on a hyperbolic (U-shaped) orbit that will never bring it through our neighborhood again.

3I/ATLAS is probably the largest and, very likely, the oldest interstellar object seen so far. While it shows many intriguing features — including large, sun-facing jets and signs of being irradiated by its billions of years spent in interstellar space — the vast majority of astronomers and space agencies agree that it is a typical comet — and not an artificial piece of alien technology, as some viral claims have suggested.

Dozens of observatories and spacecraft around the solar system have been closely monitoring 3I/ATLAS to better understand its size, trajectory, composition and origins. Studying it in depth could reveal new details about the mysterious frontier of our galaxy and how some of the earliest star systems in the Milky Way formed.

The celebrity comet 3I/ATLAS is showing itself out of our solar system for good — but not before the cosmic paparazzi at Earth's space agencies snap some of the clearest photos of it yet.

Discovered in late June and confirmed to be the third known interstellar object in July, 3I/ATLAS has spent the past several months zooming through the inner solar system at an estimated 130,000 mph (210,000 km/h). The massive, jet-spewing snowball made its closest approaches to Mars and the sun in October. It is due for its closest encounter with Earth on Dec. 19, when it will be about 170 million miles (270 million kilometers) away — nearly twice the distance between our planet and the sun.

As the comet careens toward this astronomical milestone, spacecraft managed by NASA and the European Space Agency (ESA) are snagging as many close-up observations as possible. This week, both agencies shared new images of the comet — proving that its recent flyby of the sun has left it very bright and active as it spews large amounts of sublimated gas and dust into space.

Hubble doubles down

On Thursday (Dec. 4), NASA shared the latest image of 3I/ATLAS taken by the Hubble Space Telescope. The glowing white dot at the center of the image shows the comet's nucleus (its main body) and coma, the bright atmosphere of gas and dust that wraps around the comet before getting funneled into its tail. In the background, stars are stretched into long streaks as Hubble's camera stays fixed on the fast-moving comet.

Comets typically brighten as they approach the sun, when the ice within them heats up and sublimates. Solar radiation pushes this gas into a tail that stretches away from the sun. Meanwhile, the warmest, sun-facing side of the comet may erupt with jets of gas and dust angled toward our star. Both of these features are faintly visible in the new Hubble image.

NASA snapped this image on Nov. 30, when Hubble was about 178 million miles (286 million km) from the comet. This is considerably closer than when Hubble first imaged the comet in late July. Although that first view showed little more than a blue blur, it nevertheless allowed scientists to constrain 3I/ATLAS' size to somewhere between 1,400 feet (440 meters) and 3.5 miles (5.6 km) wide — likely the largest interstellar object seen to date.

New data from this image, including details of the coma's composition, has yet to be released but is likely on the way.

ESA juices up

Also on Thursday, ESA shared its latest view of the comet, taken by the Jupiter Icy Moons Explorer (Juice) orbiter on its way to study Jupiter's moons for signs of life. Juice snapped the image Nov. 2, just days after 3I/ATLAS' close approach to the sun.

Located even closer to its target than Hubble (only 41 million miles, or 66 million km, away), Juice shows us a comet brimming with activity.

"Not only do we clearly see the glowing halo of gas surrounding the comet known as its coma, we also see a hint of two tails," an ESA spokesperson wrote in a statement. "The comet's 'plasma tail' — made up of electrically charged gas, stretches out towards the top of the frame. We may also be able to see a fainter 'dust tail' — made up of tiny solid particles — stretching to the lower left of the frame."

Earth gets ready

Juice observed 3I/ATLAS with five scientific instruments on two days. But besides this teaser image, we don't yet know what those instruments saw; the full data set won't reach Earth until late February 2026, according to ESA. That's because Juice is currently using its main antenna as a heat shield to protect it during its close pass of the sun, and relying on its smaller, less efficient antenna to beam its observations back to us.

While there's little we can learn from NASA's and ESA's new images without the full complement of scientific data, it's a good reminder that human space exploration pays off in unexpected ways. Hubble and Juice number among a dozen spacecraft that have observed 3I/ATLAS from around the solar system, including Mars rovers, solar orbiters, asteroid trackers and space telescopes that were never intended to track comets.

And there's more to come: As 3I/ATLAS draws closer to Earth, the James Webb Space Telescope will take another look at it, while countless scientific observatories and amateur astronomers will have their chance to watch it as well. When you're dealing with a mysterious intruder from parts unknown, every observation matters.

The interstellar comet 3I/ATLAS could be covered in erupting "ice volcanoes," new observations suggest.

Researchers found evidence that as the comet approached the sun, a series of cryovolcanoes (nicknamed "ice volcanoes") erupted on its surface. The activation of these icy jets can be explained by what the strange comet is made of, according to a study posted Nov. 24 to the preprint server arXiv.

The study's findings, which have yet to be peer-reviewed, suggest that comet 3I/ATLAS is similar to icy trans-Neptunian objects — dwarf planets and other objects that orbit the sun beyond Neptune. If this is confirmed, it means that despite coming from another solar system, comet 3I/ATLAS has a surprising amount in common with objects in our own cosmic neighborhood.

"We were all surprised," study lead author Josep Trigo-Rodríguez, a staff leading researcher at the Institute of Space Sciences (CSIC/IEEC) in Spain, told Live Science. "Being a comet formed in a remote planetary system, it is remarkable that the mixture of materials forming the surface of the body has resemblance with trans-Neptunian objects, bodies formed at [a] large distance from the Sun but belonging to our planetary system."

There has been endless speculation about the origins of comet 3I/ATLAS since astronomers first spotted it in July. Much of the online speculation has centered around whether this interstellar visitor could be an alien spacecraft. However, most astronomers are confident that 3I/ATLAS is a comet from an unknown star system.

Comet 3I/ATLAS is only the third interstellar object ever recorded, and offers researchers a rare opportunity to learn more about conditions around other stars and in the deep past (comet 3I/ATLAS could be billions of years older than our system). This means that scientists are scrambling to study the object before it departs our solar system forever next year.

For the new study, Trigo-Rodríguez and his colleagues studied the comet using the Joan Oró Telescope at the Montsec Observatory in the northeastern Catalonia region of Spain, pairing its observations with those made by other observatories in the region. The astronomers watched the comet carefully as it approached its closest point to our star, known as perihelion, on Oct. 29. Comets heat up as they fly closer to stars, causing ice on their surface to sublimate into gas, which researchers can then detect and study.

The researchers found that the comet entered a more intense sublimation stage when it got within about 235,000,000 miles (378 million kilometers) of the sun, while also brightening rapidly. Using the Joan Oró Telescope, they snapped the highest-resolution images yet of jets of gas and dust particles coming off the comet, which they interpreted as clear signs of cryovolcanism.

Cryovolcanoes are typically found in planetary bodies that are rich in ice, like trans-Neptunian objects. Trigo-Rodríguez noted that these planetary bodies have internal heat that melts the ice and produces the cryovolcanoes, which release vapor and dust into space.

PRE-PERIHELION STUDY OF #COMET #3IATLAS with our findings about its spectroscopic similitude with CR carbonaceous chondrites. Manuscript submitted for publication in which we propose it is a #TNO-like body experiencing #cryovolcanismNow in Cornell Univ. @arxiv repository:➡️ arxiv.org/abs/2511.19112

— @joseptrigo.bsky.social (@joseptrigo.bsky.social.bsky.social) 2025-12-02T09:08:51.972Z

In the case of comet 3I/ATLAS, the researchers believe that the cryovolcanism is driven by the corrosion of pristine material locked inside the comet. As the sun heated the comet, the threshold at which solid carbon dioxide (dry ice) sublimated into gas was breached. This then enabled an oxidizing liquid to flow into the comet's interior and react with reactive iron and nickel metallic grains and sulfides.

To test their theories about the comet's composition, the researchers ran a spectroscopic comparison (analyzing how matter interacts with light) using primitive and pristine rocky meteorites called carbonaceous chondrites that NASA collected from Antarctica.

One of these Antarctic samples contained what the researchers believe is a piece of a trans-Neptunian object. The analysis revealed that comet 3I/ATLAS was similar to these remnants from the earliest days of our solar system, and is likely rich in natural metal.

Carbonaceous chondrites are believed to have played a role in life's origins on Earth, bringing volatile materials that helped establish our atmosphere and other conditions necessary for life, according to the Natural History Museum in London.

Comet 3I/ATLAS origins

While 3I/ATLAS’s exact size is still uncertain, Hubble Space Telescope observations suggest that it's somewhere between 1,400 feet (440 meters) and 3.5 miles (5.6 kilometers) wide. Rodriguez and his colleagues calculated that if the comet is 0.6 miles (1 km) wide and has the rocky composition they suspect it has, then its mass would be more than 660 million tons (600 million metric tons).

However, even if 3I/ATLAS has a similar composition to carbonaceous chondrites and behaves like trans-Neptunian objects approaching the sun, it's still without a doubt not from our solar system. That's because of its hyperbolic trajectory, along which scientists first noticed it zooming at around 137,000 miles per hour (221,000 kilometers per hour) — too fast to be bound to our sun's gravity, according to NASA.

Researchers don't know which star system comet 3I/ATLAS originated from, but it has certainly travelled a long way. The comet is likely billions of years old and potentially more than 3 billion years older than our own solar system. In fact, the comet has spent so much time in space that it could be extremely irradiated, which would make deciphering its origins even more difficult.

Trigo-Rodríguez noted that it's important to study and track interstellar comets because they are a potential collision hazard for Earth. However, he also described them as "extraordinary objects" in their own right and worthy of consideration.

They "are space capsules, containing valuable information about the chemistry ongoing in another location of our galaxy," Trigo-Rodríguez said.

We know of three interstellar objects (ISO) that have visited our inner solar system. Oumuamua was the first one, and it came and went in 2017. 2l/Borisov, an interstellar comet, was next, appearing in 2019. And right now, the interstellar comet 3I/Atlas is enjoying a visit to the Sun-warmed inner solar system.

A massive number of ISOs must have passed through our solar system during its long, 4.6 billion year history. It's possible that some of them slammed into Earth. Maybe ISOs are responsible for some of the ancient impact craters whose remnants we can still see today, like the Vredefort impact structure.

Our solar system is much more placid than it used to be. Early in its history, it was molded by chaotic collisions. There are fewer rocks and fewer collisions now because much of the rock accreted into the terrestrial planets. But the same can't be said about ISOs. There's no reason to believe there are fewer ISOs entering our solar system than there were in the past.

That means they pose an impact risk to Earth. Is there any way to quantify that risk?

New research titled "The Distribution of Earth-Impacting Interstellar Objects" tries to understand the risk. The lead author is Darryl Seligman, an assistant professor in the Physics and Astronomy Department at Michigan State University. The paper is available online at arxiv.org.

"In this paper we calculate the expected orbital elements, radiants, and velocities of Earth-impacting interstellar objects," the authors write. Their work doesn't calculate the number of ISOs because there are no constraints on the number to work with. Their work only concerns their expected distribution.

When it comes to the source of ISOs, they focus on what are called M-star kinematics. M-stars, also known as red dwarfs, are the most numerous type of star in the Milky Way. It stands to reason that most ISOs would be ejected from M-dwarf solar systems purely based on numbers. However, the authors admit this is somewhat arbitrary. "This choice is admittedly somewhat arbitrary because the kinematics of interstellar objects is unconstrained," they explain.

The researchers used simulations to try to understand the problem. "We generate a synthetic population of ~10¹⁰ interstellar objects with M-star kinematics in order to obtain ~10⁴ Earth-impactors," the researchers write. Their simulations show that ISOs are twice as likely to come from two directions: the solar apex and the galactic plane.

The solar apex is the direction the Sun follows relative to its solar neighborhood. Basically, it's the Sun's path through the Milky Way. ISOs are more likely to come from the solar apex because the solar system is moving in that direction. It's like driving in a car and hitting more raindrops.

The galactic plane is the flat, disk-shaped region that the Milky Way occupies. Since it's where most of the other stars are, ISOs are likely to come from this region. ISOs approaching from ahead have a higher collisional cross-section.

The simulations also show that ISOs from the solar apex and the galactic plane would have higher velocities. But counterintuitively, the ones that could impact Earth have slower velocities. This is because the subset of ISOs that can impact Earth have a tendency to be low-eccentricity hyperbolic bodies. The Sun's gravity has a greater effect on these objects and can preferentially capture slower moving objects and shift them into Earth-crossing trajectories.

The seasons make a difference, too. ISOs with the highest impact velocity are more likely to arrive in the Spring, because Earth is moving toward the solar apex. But winter has more frequent potential impactors because at that time Earth is positioned toward the solar antapex, the place the Sun is moving away from.

When it comes to what part of Earth is most at risk of an ISO impactor, low latitudes near the equator face the greatest risk. There's also a slightly elevated risk of impact in the northern hemisphere, where almost 90% of the human population lives.

As explained earlier, this work is only for ISOs ejected from M-dwarf systems. "These distributions are only applicable for interstellar objects that have M-stars kinematics. Different assumed kinematics should change the distributions presented in this paper," the authors explain. But they also point out that the main points in their work likely apply to other kinematics. "The salient features summarized in this section presumably also apply to different kinematics, perhaps to a muted or more distinct overall effect," the researchers write.

It bears repeating that this work doesn't predict the number of ISOs. There's no way to measure that. "In this paper we intentionally do not make any definitive predictions about the rates of interstellar impactors," the authors write in their conclusion.

But the results do feed into future observations with the Vera Rubin Observatory and its Legacy Survey of Space and Time. It gives astronomers and idea about the distribution of ISOs that should be deteced by the VRO.

We're just opening our eyes to the idea of ISOs. This paper gives us an idea of where Earth-impacting ISOs are likely to arrive from, when they're most likely to impact, and where they're most likely to impact. Once the VRO and its LSST get going, astronomers will begin to acquire data that will either support or undermine these findings.

The original version of this article was published on Universe Today.

In space, death can be a beautiful thing. That's certainly the case for the recently deceased "other" comet ATLAS, which is slowly breaking apart after meeting its explosive end earlier this month, stunning new images reveal.

C/2025 K1 (ATLAS) is a comet originating from the Oort Cloud beyond Neptune that was discovered in May by astronomers at the Asteroid Terrestrial-impact Last Alert System (ATLAS). It reached its closest point to the sun, or perihelion, on Oct. 8, coming within 31 million miles (50 million kilometers) of our home star. But the comet largely went under the radar until earlier this month, when it developed a rare golden glow in its coma and tail.

It has become known as the "other ATLAS," thanks to its shared surname with the interstellar comet 3I/ATLAS, which has been dominating headlines since it was first spotted shooting through the solar system in July. The two comets have no relation, other than being detected by the same telescope network around the same time.

On Nov. 13, astronomers noticed that C/2025 K1 had broken apart into several pieces. Austrian astrophotographer Michael Jäger has been keeping a close eye on C/2025 K1 since it began to fall apart, and he has now shared a stunning timelapse animation that shows the fragments of the comet slowly separating from one another.

"Following brightness surges in early November, we have been able to observe this comet splitting into three brighter fragments for the past two weeks," Jäger told Spaceweather.com. "The animation shows it on November 12, 14, 18, 19, and 20th."

The comet was not expected to survive its perihelion — astronomers predicted that the close proximity of its journey around the sun would place a huge amount of gravitational strain on the object. After its solar flyby, initial observations suggested that it had emerged unscathed. However, following a sudden brightening event, the comet then broke apart into three distinct pieces.

More recent photos have shown that a smaller fourth fragment also splintered from the comet, according to Spaceweather.com. However, this part of the comet is not visible in the new animation.

C/2025 K1 was one of just a handful of comets that have ever been seen with a golden hue (see below), which is likely the result of a surprising lack of carbon-bearing molecules, such as dicarbon, carbon monoxide and cyanide in its nucleus. In fact, only two other known comets have ever had fewer of these molecules, astronomer David Schleicher of Arizona's Lowell Observatory recently reported.

Researchers had hoped to learn more about the comet and its surprising composition during its closest approach to Earth on Tuesday (Nov. 25). However, this now seems unlikely.

But the comet's fragments will still be visible in the constellation Leo to anyone with a decent telescope or a pair of stargazing binoculars.

Other ATLAS(s)

C/2025 K1 is not the first comet to bear the name ATLAS. In fact, dozens of other comets have been found by the Asteroid Terrestrial-impact Last Alert System — a NASA-funded robotic survey, which has been scanning the night sky using telescopes in Hawaii, South Africa and Chile since 2015.

Over the last few years, several ATLAS comets have made the news, including C/2024 G3, which appeared in spectacular snaps by astronauts onboard the International Space Station (ISS) earlier this year, as well as a doomed sungrazer comet, the Halloween ATLAS comet and Comet Tsuchinshan-ATLAS, which all shone brightly in 2024.

But the most famous of the ATLASs is 3I/ATLAS, an alien comet that is traveling past us after being ejected from its own star system, potentially long before the solar system was born.

3I/ATLAS is currently on its way back out of the solar system, having reached its own perihelion on Oct. 29, and will reach its closest point to Earth on Dec. 19, when it will reach a minimum distance of 168 million miles (270 million km) from our planet. And despite what some people claim, the astronomical community is very much in agreement that it is not an alien spacecraft.

Only time will tell what wonders the future ATLAS comets will have in store for us.

NASA has released a treasure trove of comet 3I/ATLAS images, giving us some of the closest views yet of the interstellar visitor.

The U.S. government shutdown, which ran from Oct. 1 to Nov. 12, delayed the release of the highly anticipated images, which include snaps taken from instruments around Mars and the sun over the past several months.

Live Science has rounded up some stand-out shots from the comet 3I/ATLAST image drop for you to enjoy below, while the full gallery is available on NASA's website.

The High Resolution Imaging Science Experiment (HiRISE) captured this image of the comet from aboard NASA's Mars Reconnaissance Orbiter (MRO). The imager caught sight of comet 3I/ATLAS as the comet zoomed past Mars in early October.

While the comet was much closer to Mars in October than it will ever get to Earth, it still wasn't that close. This image was taken when the comet was around 19 million miles (30 million kilometers) from MRO. For reference, the moon's average distance from Earth is about 239,000 miles (384,000 km). The bright dot represents the comet's main body, or nucleus, while the diffuse cloud of particles around it is 3I/ATLAS' coma — a feature characteristic of most comets that get heated up by the sun while flying through our solar system.

The Mars Atmosphere and Volatile Evolution (MAVEN) orbiter got this trippy ultraviolet image of comet 3I/ATLAS near Mars (relatively speaking) on Sep. 28. MAVEN's Imaging Ultraviolet Spectrograph takes advantage of the ultraviolet part of the light spectrum to decipher the chemical composition of objects, according to NASA.

The blue in the image is hydrogen. The blue dot on the left represents hydrogen emitted from comet 3I/ATLAS, while the bright blue on the right is the hydrogen emitted by Mars. The dim blue oval in the middle is background hydrogen flowing through the solar system between planets. Researchers hope to use observations like this one to better understand the comet's makeup.

NASA released this GIF of comet 3I/ATLAS, created using images taken by the Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission between Sept. 28 and Oct. 10. The PUNCH mission is made up of four small satellites in low-Earth orbit, focused on the sun. Comet 3I/ATLAS is the white dot in the center image, moving through a stream of blurred light from stars. The bright blob that flashes past the comet is Mars.

Comet 3I/ATLAS is pretty in pink in this observation, thanks to colorized images from the Solar Terrestrial Relations Observatory spacecraft (STEREO-A). The Heliocentric Imager-1 (H1) instrument aboard STEREO-A captured the image in visible light, which was then subsequently colorized to differentiate it from other spacecraft images, according to NASA.

Another image taken by a solar orbiter, this time from the European Space Agency and NASA's Solar and Heliospheric Observatory (SOHO). The SOHO mission launched all the way back in 1995 and is the longest-serving sun satellite yet, according to NASA. SOHO snapped this image of comet 3I/ATLAS between Oct. 15 and Oct. 26, while the comet was brightening on the way to its closest encounter with the sun.

This last GIF isn't particularly impressive to look at, but it was taken from the Martian surface, which is pretty cool if you ask us. NASA's Perseverance rover looked up to observe the comet fly by the Red Planet on Oct. 4. Perseverance was investigating Jezero Crater at the time, searching for ancient signs of life.

Since the discovery of comet 3I/ATLAS in July, there has been much speculation that this interstellar visitor could be an alien spacecraft. However, most astronomers are confident that 3I/ATLAS is a natural comet from an unknown star system. NASA was keen to stress that the comet was of natural origins when it presented the new images during a stream on Wednesday (Nov. 19).

"This object is a comet," NASA Associate Administrator Amit Kshatriya said during the stream. "It looks and behaves like a comet… and all evidence points to it being a comet. But this one came from outside the solar system, which makes it fascinating, exciting and scientifically very important."

NASA has finally released a cache of previously unseen images of comet 3I/ATLAS, as the space agency stresses that the interstellar visitor is a natural object.

Comet 3I/ATLAS has become a celestial celebrity since its discovery in July, in part because of endless speculation that it could be an alien spacecraft. While most astronomers are confident that the interstellar visitor is a natural comet from an unknown star system, NASA has been silent on the comet in recent weeks due to the U.S. government shutdown.

The shutdown, which ran from Oct. 1 to Nov. 12, coincided with comet 3I/ATLAS flying behind the far side of the sun, reaching its closest point to the sun (perihelion) on Oct. 29 and entering its most active phase. NASA’s delay in releasing the new images during this period fueled conspiracy theories, with some speculating that the government agency had something to hide.

When NASA hosted a Wednesday (Nov. 19) stream to present the highly anticipated images, it came out swinging. Soon after the conference began, NASA Associate Administrator Amit Kshatriya said he wanted to address what he described as "the rumors."

"This object is a comet," Kshatriya said. "It looks and behaves like a comet… and all evidence points to it being a comet. But this one came from outside the solar system, which makes it fascinating, exciting and scientifically very important."

The comet's natural origins shouldn't detract from 3I/ATLAS’s story. This object is only the third interstellar comet ever recorded, potentially the oldest comet ever seen and the most massive of its kind, so there are plenty of non-alien reasons for it to be of interest to humanity.

The new images were taken using a variety of different instruments, with the closest shots coming from NASA's Mars Reconnaissance Orbiter. This spacecraft has been orbiting Mars since 2006, searching for signs of water on the Red Planet with its onboard High Resolution Imaging Science Experiment (HiRISE). The imager snapped comet 3I/ATLAS as it zoomed past Mars in early October.

The Mars Atmosphere and Volatile Evolution (MAVEN) orbiter also captured ultraviolet images of comet 3I/ATLAS that will help researchers better understand the comet's makeup, according to NASA.

Elsewhere, sun-monitoring instruments like NASA's Solar Terrestrial Relations Observatory (STEREO) and the asteroid-chasing Psyche and Lucy spacecraft caught additional new glimpses of comet 3I/ATLAS. The space agency noted that these observations will provide details on the comet's tail. However, the images have only just been processed and are only now being studied, so findings from them thus far are limited.

The interstellar interloper originated somewhere beyond our solar system. Researchers don't know which star system it came from, but it could be billions of years old — potentially more than 3 billion years older than our sun.

While the comet's age has yet to be confirmed, Tom Statler, lead scientist for solar system small bodies at NASA's Planetary Science Division, said that because the comet is zooming along three times faster than the average rate at which stars in our cosmic neighborhood orbit the Milky Way’s center, it has likely been in interstellar space for a very long time.

"We can't say this for sure, but the likelihood is it came from a solar system older than our own solar system," Statler said during the stream. "Which gives me goosebumps to think about frankly, because that means that 3I/ATLAS is not just a window into another solar system; it's a window into the deep past, and so deep in the past that it predates even the formation of our Earth and our sun."

An astrophotographer has snapped a stunning shot of the interstellar visitor 3I/ATLAS photobombing a distant galaxy in the night sky. The remarkable image, which also captured the comet's multiple tails, is a reminder of the object's otherworldly nature — but that doesn't mean it was made by aliens, the photographer insists.

Satoru Murata, a New Mexico-based photographer who has previously worked on multiple astronomical research projects, captured the new image using a 0.2-meter (0.7 feet) telescope on Sunday (Nov. 16) shortly before sunrise. It shows a familiar green glow coming from 3I/ATLAS's coma, along with the comet's long ion tail and the reemergence of its shorter anti-tail, which is likely caused by excess dust blowing off its surface. In recent weeks, the comet briefly appeared to lose both these tails, although this was an optical illusion due to its position relative to Earth.

Eagle-eyed observers may also be able to see several smaller jets of gas shooting outward from the comet's coma. These are the result of "outgassing," which occurs when solar radiation heats comets' icy interiors, causing gasses to shoot out of cracks in their icy shells. This natural process provides a small amount of non-gravitational acceleration to the comet and was the basis of a recent rumor that wrongly claimed 3I/ATLAS had exploded.

In the top left of the image is the barred spiral galaxy NGC 4691, which is located around 70 million light-years from Earth. Seeing the interstellar comet alongside NGC 4691 "really gave the impression of the object being from another world," Murata wrote in a recent Facebook post. (However, the comet originated from a star system within the Milky Way, not another galaxy.)

While this new photo has given us an impressive glimpse of 3I/ATLAS, astronomers are eagerly awaiting new high-definition NASA photos of the comet, which will be released on Wednesday (Nov. 19). These images were captured by NASA's Mars Reconnaissance Orbiter during the comet's close flyby of the Red Planet on Oct. 3 but have remained unreleased due to the recent government shutdown.

On Friday (Nov. 14), the European Space Agency revealed that its own Mars photos had helped researchers narrow down 3I/ATLAS's predicted trajectory through the solar system.

Interstellar visitor

3I/ATLAS is the third interstellar object discovered to date and was first spotted in early July, shooting toward the sun at more than 130,000 mph (210,000 km/h). It likely originates from the "frontier" region of the Milky Way and could be up to 7 billion years old, making it significantly older than our solar system.

The comet recently reemerged from behind the sun's far-side relative to Earth, where it reached its closest point to our home star on Oct. 29. The trip around the sun was eventful, with 3I/ATLAS experiencing an unexpected brightening event and a temporary color change. The comet has also displayed several other anomalous characteristics in recent months, including a highly irradiated surface and an overabundance of certain chemicals.

These unusual traits have led some researchers to controversially propose that 3I/ATLAS might be an alien spaceship in disguise. However, the majority of the astronomical community agrees that the object is almost certainly a comet. (Similar claims were also made about the first interstellar object 'Oumuamua, which was discovered in 2017 and is most likely an asteroid.)

Murata, too, is certain of 3I/ATLAS's cometary status.

"No, it's not an alien mothership, and the probability that it's any type of object created by extraterrestrial civilization is close to zero," he wrote in an Instagram post about the new photo. "As people have said, if it looks like a duck and behaves like a duck, it's a duck."

3I/ATLAS will reach its closest point to Earth on Dec. 19, when it will reach a minimum distance of 168 million miles (270 million km) from our planet.

Earthlings will soon have their chance to see NASA's clearest images yet of the interstellar comet 3I/ATLAS, and you can watch it right here.

The space agency recently announced a live news teleconference to take place today (Nov. 19) at 3 p.m. EST, during which NASA scientists and administrators will share and discuss never-before-seen images of the interstellar comet taken by telescopes and spacecraft over the past month or so.

The images will be posted to this NASA page shortly after the event starts, and we will also be covering the latest updates on our live blog.

Why now?

These images have yet to be shared with the public, as a majority of NASA personnel were furloughed during the U.S. government shutdown from Oct. 1 to Nov. 12, preventing the agency from communicating with the public.

It was an unlucky time for NASA to go silent, as comet 3I/ATLAS passed several huge milestones on its one-way trip through our solar system during that period. On Oct. 29, the interstellar comet made its closest approach to the sun, entering its brightest and most active phase as its surface ices started to melt and sublimate (shift from a solid to a gas).

And earlier, on Oct. 3 — just days after the government shutdown began — the comet made its closest approach to Mars, passing within just 19 million miles (30 million kilometers) of the Red Planet and the fleet of NASA and European Space Agency (ESA) spacecraft stationed there. That may sound like a comically vast distance, but it's the closest look we're likely to get of the interstellar interloper; 3I/ATLAS will get no closer than 170 million miles (270 million km) of Earth at its closest approach to our planet on Dec. 19, according to NASA.

The closest views of 3I/ATLAS so far

On Oct. 7, ESA released its own closest images of the comet taken so far, captured by its ExoMars Trace Gas Orbiter (TGO) and Mars Express orbiter. However, both of these spacecraft were designed to observe the surface of Mars just a few hundred miles below, not to track high-speed objects millions of miles away. The comet appears as little more than a bright, slinking blur in ESA's images — but, the observations confirmed that 3I/ATLAS bore the telltale cloud of ionized gas (a coma) that's characteristic of natural comets.

ESA scientists also compared the Mars orbiter data with observations from Earth telescopes, allowing them to better triangulate the comet's exact position and significantly narrow down its path through our solar system.

During the news conference, NASA is expected to share images taken by its Mars Reconnaissance Orbiter's HiRISE camera from the days before and after the comet's close approach to Mars, as well as observations from other telescopes, according to the agency's latest announcement.

The live stream will be hosted on the agency's website as well as on YouTube and Amazon Prime. Members of the public are invited to submit questions via the hashtag #AskNASA on social media, some of which may be addressed live on air.

Comet 3I/ATLAS was discovered in late June and confirmed to be an interstellar object in early July. It originates from an unknown star system far beyond our own, and is just the third object of its kind ever detected. Many mysteries about its nature and origins still remain, and dozens of observations from Earth and space-based telescopes are expected to come as the comet barrels toward its closest approach to Earth next month. Spacecraft near Jupiter will also observe it early next year, as the comet makes its final exit from our solar system.

Editor's note: This article was updated on Wednesday (Nov. 19) to indicate that the live stream is today

Researchers have narrowed down the exact route that the interstellar interloper 3I/ATLAS will take as it begins its one-way trip out of the solar system.

Thanks to data collected from the alien comet's recent close flyby of Mars, scientists at the European Space Agency (ESA) have refined the comet’s trajectory by ten-fold. And this could better help researchers unravel its secrets in the coming months, experts say.

3I/ATLAS is an interstellar object — the third of its kind ever seen — that was first spotted in early July, shooting toward the sun at more than 130,000 mph (210,000 km/h). It is a comet that was likely ejected from a star in the "frontier" region of the Milky Way up to 7 billion years ago. Scientists have observed a number of strange characteristics of the comet, including a highly irradiated surface and a puzzling anti-tail. This has led to wild rumors that 3I/ATLAS might be an alien spacecraft, which the majority of astronomers agree are almost certainly untrue.

After passing its closest point to the sun on Oct. 29, 3I/ATLAS has recently reemerged from behind the sun's far-side relative to Earth. The trip around the sun was an eventful one: with the comet experiencing an unexpected brightening event, a temporary color change and a brief vanishing of its tail.

But before this, the comet also had a close encounter with Mars, coming within 18.6 million miles (30 million kilometers) of the Red Planet on Oct. 3.

During the Mars flyby, the European Space Agency's (ESA) ExoMars Trace Gas Orbiter managed to snap highly detailed photos of 3I/ATLAS streaking toward the sun. By analyzing the orbiter's data from this encounter, ESA scientists have improved predictions of 3I/ATLAS's exit trajectory out of the solar system with a surprising level of success.

"While the scientists initially anticipated a modest improvement, the result was an impressive ten-fold leap in accuracy, reducing the uncertainty of the object’s location," ESA representatives wrote in a statement. "The improved trajectory allows astronomers to aim their instruments with confidence, enabling more detailed science of the third interstellar object ever detected."

Before now, researchers have been relying solely on ground-based observatories or Earth-orbiting spacecraft to track 3I/ATLAS's position, which only provides specific views of the anomalous object. But by using observations from Mars, the ESA team could better "triangulate" the comet's position, similar to how intelligence agencies track mobile phones using multiple cell towers.

However, factoring in the orbiter's precise movements around Mars relative to the comet's trajectory was no easy task. To make the process harder, the spacecraft's Colour and Stereo Surface Imaging System (CaSSIS) is designed to photograph the Red Planet's surface, not objects in space, the researchers wrote.

In fact, the method of imaging space objects with planetary orbiters is so hard that this is the first time that data from one of these spacecraft has been accepted into the International Astronomical Union's Minor Planet Center database, which tracks the movements of all near-Earth objects, researchers wrote.

ESA is now hoping to repeat the trick with its Jupiter Icy Moons Explorer (JUICE), which will get a good look at 3I/ATLAS later this month, researchers wrote. The agency's researchers have also previously suggested that two of its other spacecraft, Hera and Europa Clipper, could also pass through the comet's tail as it moves away from the sun.

During the recent Mars flyby, NASA's Mars Reconnaissance Orbiter also captured what could potentially be the best ever image of 3I/ATLAS, which some researchers predict could reveal more about its features. Due to the recent government shutdown, NASA has yet to release these images to the public. But recent reports suggest that these images could be released any day now.

3I/ATLAS will reach its closest point to Earth on Dec. 19, when it will reach a minimum distance of 168 million miles (270 million km) from our planet.

The "other" Comet ATLAS has fragmented, transforming into a cloud of debris that's streaming into space, new observations have revealed.

The comet, called C/2025 K1 (ATLAS), was discovered in May by astronomers at the Asteroid Terrestrial-impact Last Alert System (ATLAS) and passed perihelion, or closest point to the sun, on Oct. 8. It has no relation to the famous interstellar comet 3I/ATLAS, other than having been discovered by the same telescope network around the same time.

Initial observations appeared to suggest that Comet K1 survived its passage around our star at a minimum distance of 31 million miles (50 million kilometers), or roughly four times closer than Comet 3I/ATLAS got.

However, new observations taken by astronomer Gianluca Masi in Manciano, Italy, show that the gravitational strain of its voyage around the sun was too much for the comet, causing it to fragment into several pieces, or clouds.

"Several parts (sub-nuclei or clouds of debris) are visible, also a plume just below the leading (the first from the left) fragment," Masi, an astronomer at the Astronomical Observatory of Campo Catino and the founder of The Virtual Telescope Project, wrote in an update.

C/2025 K1's disintegration was portended by a sudden brightening event around perihelion, which saw the comet transform from the greenish hue seen in many comets that fly close to our sun (caused by the presence of diatomic carbon fluorescing in sunlight) into a streaking ribbon of gold.

The cause of this transformation is unclear; some scientists speculate that the change in color had something to do with a relative lack of carbon-bearing molecules in the comet's coma (the cloud of ice, gas and dust around the comet's body).

If you want to see the exploded comet for yourself, look in the constellation Leo, where it's shining at magnitude 9.9, according to The Sky Live. (In astronomy, a lower magnitude corresponds to a brighter object; Regulus, the brightest star in Leo, has an apparent magnitude of about 1.35, for example.) Although the comet is still too dim to be seen with the naked eye, it can be spotted with a good telescope or a pair of stargazing binoculars.

Whatever survives of the comet is set to pass closest to Earth on Nov. 25. It will come within about 37 million miles (60 million km), or just under half the average distance between Earth and the sun.

Astronomers have detected the first-ever "radio signal" coming from the interstellar comet 3I/ATLAS, right as it passed the halfway mark on its oneway trip through the solar system. And while this may seem like ostensible proof of the comet’s supposed alien origins — it's actually the complete opposite.

3I/ATLAS is the third-known interstellar object (ISO) to pass through our cosmic neighborhood. It was first spotted in early July, speeding toward the sun at more than 130,000 mph (210,000 km/h), although observations dating back to May have since been uncovered. Most researchers agree that it is a comet, potentially the oldest of its kind ever seen, that was catapulted out of an alien star system in the "frontier" region of the Milky Way up to 7 billion years ago.

However, ever since the interstellar interloper was discovered, a small group of scientists — led by Harvard University astrophysicist and renowned alien-hunter Avi Loeb — have been promoting the unevidenced theory that the comet is actually an alien spacecraft in disguise. This has led to a number of misleading stories about the comet, which experts say distracts from the real science surrounding the ISO. (This is similar to what happened to the first-ever ISO 'Oumumua, which Loeb and others also labelled as a potential alien mothership.)

So, when astronomers at South Africa's MeerKAT radio telescope recently announced that they had detected the first radio emissions from 3I/ATLAS, proponents of Loeb's theory were probably expecting to find evidence of some covert alien transmission, especially as it coincided with the comet's closest approach to the sun, or perihelion, which occurred on Oct. 29.

But the signals did not have a technological origin. Instead, they are the result of specific wavelength absorption related to the presence of hydroxyl radicals, or OH molecules, in the comet's coma.

These radicals are formed by the breakdown of water molecules as they are ejected from the comet via a natural process known as outgassing, which is a clear sign of cometary activity, according to a 2016 study.

This is not the first time that astronomers have seen evidence of water coming from 3I/ATLAS: In early October, NASA researchers spotted water spewing from the comet "like a fire hose" on full blast. But the latest findings show that this water is being broken down by solar radiation —as you would expect during perihelion.

Loeb acknowledged the detection of the hydroxyl radicals in the latest 3I/ATLAS update on his personal blog, which now has over 100,000 subscribers. However, he did not state whether this was a sign of classic cometary activity or not.

The new radio signals were first detected on Oct. 24, shortly after 3I/ATLAS briefly disappeared behind the sun during perihelion. The comet's solar flyby was also notable for an unexpected brightening event and a temporary color change. And after reappearing earlier this month, the comet then appeared to have lost its tail, although this turned out not to be true.

The comet has previously displayed several other anomalous characteristics that have added fuel to the fires of alien conspiracy theorists, including a highly irradiated surface, an overabundance of carbon dioxide and a puzzling anti-tail. However, all of these traits have been properly explained by the astronomical community, which is almost unanimously convinced that 3I/ATLAS is a natural object.

A separate yet connected alien theory was also squashed this week when astronomers detected an "almost interstellar object" that reached its closest point to Earth on Tuesday (Nov. 11). Rumors suggested that it could have been a probe deployed by 3I/ATLAS during perihelion, but this was quickly trashed, with even Loeb admitting the claim was unlikely. Instead, the newly discovered object, dubbed C/2025 V1 (Borisov) is a typical solar system comet.

Other reports, which cited Loeb's calculations on 3I/ATLAS's non-gravitational acceleration, also suggested that the comet may have exploded due to its supposedly excessive loss of mass. However, recent observations have proved that this is not the case either.

Comet 3I/ATLAS lovers don't despair: Our favourite interstellar visitor most likely didn’t just explode, an expert says after examining the latest observations.

Yesterday (Nov. 10), Futurism reported that comet 3I/ATLAS may have broken into pieces after re-emerging from behind the far side of the sun. The science and technology website quoted the blog of Harvard University astrophysicist Avi Loeb, who calculated that the comet lost a lot of mass based on a 3I/ATLAS image captured by two small telescopes in Spain on Sunday (Nov 9).

However, Loeb's assessments of 3I/ATLAS have come under increased scrutiny in recent days. He was once again using his blog to speculate that the comet could be an alien spaceship. Yet most researchers are confident it's a natural object, and that it hasn’t, as a matter of fact, exploded.

"All the images I've seen show a fairly ordinary/healthy-looking comet," Qicheng Zhang, a postdoctoral fellow at the Lowell Observatory in Arizona who has been studying the comet, told Live Science in an email. "There's no sign at all that the nucleus broke apart."

Comet 3I/ATLAS recently disappeared (briefly) behind the sun, reaching its closest point to our star, known as perihelion, on Thursday (Oct. 29). As it reemerges, astronomers are eagerly watching it to learn more about its makeup. That’s because comets heat up as they fly closer to stars, causing ice on their surface to sublimate into gas which researchers can then detect and study.

That newly unleashed gas can burst through the comet’s surface in gargantuan jets, wrap around the comet’s body in a cloud called a coma, or be swept away into the comet’s long tail. All of these features are made brighter by the sun’s ionizing radiation, allowing even amateur astronomers to study the comet under the right conditions.

From Earth's perspective, the comet is currently rising higher and higher above the eastern horizon and, with the right conditions, is visible through a small telescope (6-inch lens) in much of the Northern Hemisphere.

And everyone is sure to be looking. Comet 3I/ATLAS has become a lightning rod of celestial speculation since its discovery in July, with Loeb and others suggesting that the comet — an interstellar visitor from beyond our solar system that’s thought to be more than 7 billion years old — might be an alien probe.

Yet most astronomers are confident that the interstellar visitor is a natural comet from an unknown star system in the Milky Way. The comet’s natural origins should be cause for excitement, not disappointment: 3I/ATLAS is only the third interstellar comet ever recorded, is the most massive of its kind, and potentially the oldest comet ever seen.

In an image taken by amateur astronomers Michael Buechner and Frank Niebling on Sunday (Nov. 9), jets appear to be shooting off the comet. This led Loeb to use an estimate of the amount of jetted material and the comet's corresponding mass to claim that it would have needed a much larger surface area than has been observed if it were a natural object.

Loeb's assessment also claimed that the comet should have broken up into at least 16 pieces — so if astronomers find that it hasn't broken up in upcoming observations, Loeb thinks scientists will have to consider that it isn't a natural comet.

To put it lightly, astronomers disagree.

"I checked Avi Loeb's blog, and it sounds like he's just built a house of cards on top of his unfounded claim about the comet's acceleration, which was an egregious misinterpretation of the comet's orbital parameters anyone who's ever computed any comet's orbit will immediately recognize as faulty," Zhang said.

Before his latest post, Loeb’s claims were already drawing strong criticisms from astronomers. On Sunday, Jason T Wright, a professor of astronomy and astrophysics at Penn State University, wrote in his blog that there weren't any indications that 3I/ATLAS was an alien spacecraft, breaking down ten of Loeb’s claims about unnatural “anomalies” point by point. He also questioned Loeb's expertise and criticised his posts and papers.

"In these papers and on his blog he regularly betrays an unfamiliarity with well-established planetary science concepts and misinterprets papers and comes to erroneous conclusions," Wright wrote.

3I/ATLAS will make its closest approach to Earth on Dec. 19. Until then, expect many more new observations and claims — just take them with a grain of salt.

A never-before-seen comet that shares some minor similarities with the infamous interstellar object 3I/ATLAS is about to make its closest approach to our planet just a few days after it was first spotted speeding toward us.

However, despite some suggestions to the contrary, the newly discovered comet is not related to our current interstellar visitor, and almost certainly originated within the solar system.

The new comet, named C/2025 V1 (Borisov), was first spotted on Nov. 2 by the Crimea-based amateur astronomer Gennadiy Borisov. It will reach its closest point to Earth on Tuesday (Nov. 11), when it will reach a minimum distance of 64 million miles (103 million kilometers) from our planet, or around 270 times further away than the moon, according to Orbital Today. It is set to reach its closest point to the sun, or perihelion, on Sunday (Nov. 16).

C/2025 V1 has an apparent magnitude of around 13.8, making it too faint to be seen with the naked eye. However, the new comet may be visible to stargazers with a decent telescope or a pair of stargazing binoculars. It is currently located in the constellation Virgo and is most clearly visible just before sunrise, according to TheSkyLive.com.

If the name "Borisov" rings a bell, it’s because Gennadiy Borisov also discovered the second-known interstellar object (ISO), dubbed "Comet Borisov," in 2019. Like 3I/ATLAS, which was first spotted in early July, this alien comet was ejected by a faraway star in the Milky Way and sailed through space for billions of years before coincidentally shooting right through our cosmic neighborhood at incredibly high speeds.

This association, along with some additional anomalous characteristics, was enough for some to draw comparisons between C/2025 V1 and 3I/ATLAS. They included the renowned Harvard University astrophysicist and alien-hunter Avi Loeb, who described it as a "nearly interstellar object" in a recent blog post.

How can an object be "nearly interstellar"? It comes down to its orbit. C/2025 V1 is slightly unusual, given its high eccentricity, meaning that it is traveling toward the sun along a very straight trajectory. This is similar to, although not as extreme as, the trajectory of 3I/ATLAS — and is the main reason for the latest comparisons, Loeb wrote. Like in some recent photos of 3I/ATLAS, the new comet also appears to be missing its tail, he added.

C/2025 V1 was discovered while 3I/ATLAS was still temporarily hidden from us, due to it being positioned on the opposite side of the sun to Earth. This has led some new outlets to speculate that C/2025 V1 could be an alien probe that was secretly deployed by its "mothership" 3I/ATLAS, which is a theory that was first postulated by Loeb shortly after the latest ISO was discovered.

However, in his latest post, Loeb downplayed this idea, writing that "C/2025 V1 is not related to 3I/ATLAS if it did not employ non-gravitational propulsion." The distance between the two objects at their minimum separation was also around 140 million miles (225 million km), which is likely too great to explain an association between them, he added.

Instead, the new comet likely originates from the Oort Cloud — a giant reservoir of comets and other icy objects located near the outer edge of the solar system. However, its origin point and orbital trajectory have not yet been properly calculated.

As for 3I/ATLAS, the alien comet has now reappeared from its short stint behind the sun, having reached perihelion on Oct. 29. This solar flyby was notable for several other reasons, including an unexpected brightening event and a temporary color change. It has now started its journey back out of the solar system and will reach its closest point to Earth on Dec. 19.

The ISO has displayed a number of other anomalous characteristics, including a highly irradiated surface and a puzzling anti-tail. However, despite what some people claim, there is no reliable evidence that 3I/ATLAS is anything other than a comet — just like C/2025 V1.

On October 29, Comet 3I/ATLAS reached its closest point to the sun.

This point, known as perihelion, was around 210 million kilometers from the sun, or 1.4 times the distance between the sun and Earth, and it was on the opposite side of the sun to Earth. This means the sun had been blocking the comet from our view (from Earth). Now, ground telescopes have begun watching it again.

The comet is the third interstellar object (hence the "3I") we've detected flying through our Solar System.

When it was first detected on July 1 2025 by the Asteroid Terrestrial Last Alert System (or "ATLAS"), one of the first questions people asked was "but is it aliens?".

This isn't the first time the alien question has come up in the context of a new astronomical discovery. But although it might be fun, it can also detract from the real (and very cool) science, and fuel misinformation.

A long history of speculation

Similar alien speculation arose when the first two interstellar objects were discovered: 1I/2017 U1 'Oumuamua and Comet 2I/Borisov.

And it doesn't just happen for interstellar objects.

In 2019, I wrote my first public article about a discovery I made as a PhD student. I had found radio light coming from a binary star system, the first object found by the MeerKAT telescope to be changing brightness over time. Even though this had nothing to do with aliens, the editor asked me to include speculation about them.

In 1967, Jocelyn Bell Burnell, then a PhD student, discovered a rapidly repeating flash of radio light.

As a joke, she labelled it LGM 1 for "Little Green Men", but the astronomers working on it did not really believe they had discovered aliens. They were, however, concerned about the possibility that alien-related media coverage would sensationalize the discovery and hinder their scientific investigations.

A 7 billion-year-old visitor

This concern remains for astronomers today.

Comet 3I/ATLAS is possibly the oldest thing we've ever seen in our Solar System. Our Solar System formed 4.6 billion years ago, while recent research points to Comet 3I/ATLAS possibly being more than 7 billion years old.

It has spent a lot of that time zipping through the universe just to spend a few months in our Solar System. When the comet reached perihelion, that's probably the closest it's been to a star in at least millions of years.

Research has shown the comet has more carbon dioxide in its outer layers than has been seen in most comets in our Solar System. It also has a higher ratio of nickel to other elements than has been seen in local comets.

These chemical signatures give us a unique insight into the chemical composition of the cloud of gas that formed the solar system where the comet came from.

This is one of the key reasons why we should only be asking about aliens when all other possibilities are exhausted. When we talk about aliens first, we might miss all this amazing information.

As astronomer Carl Sagan said (in his rewording of a principle by French mathematician Pierre-Simon Laplace), "extraordinary claims require extraordinary evidence". It's true we can't completely explain every detail of the comet yet, but not knowing everything is not evidence of aliens.

Embrace the uncertainties

Talking about aliens also leaves room for misinformation to spread.

For example, there have been claims of things such as trajectory shifts and Comet 3I/ATLAS "hiding" behind the sun. Despite no evidence to support this, I received many questions along these lines when I spoke about the comet online. This demonstrates how easy it is for misinformation to be generated and spread when we're talking about "aliens".

There are ways to see the comet while it's on the other side of the sun. For example, the European Space Agency plans to observe the comet using the Mars Express, ExoMars Trace Gas Orbiter and the Jupiter Icy Moons Explorer.

And if you'd like to see the trajectory of Comet 3I/ATLAS and find out where it is right now, you can.

There might be something to be learned from poets here. Romantic poet John Keats wrote about something he called "negative capability". It's a strange name, but the concept is about being able to sit with "uncertainties, mysteries and doubts" and be content with not knowing.

There's a lot we don't know about Comet 3I/ATLAS and about the universe. It wouldn't be much fun to be an astronomer if we knew everything already. But when there's something unknown, we humans like to fill that gap.

For astronomy mysteries, the gap tends to be filled with aliens. However, not knowing all the answers is not proof of aliens. It just means that we have work to do.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

A new image of comet 3I/ATLAS has revealed that the interstellar visitor is glowing green and hiding its tail, but that doesn't mean there's anything wrong with it.

Qicheng Zhang, a researcher at the Lowell Observatory in Arizona, used the observatory's powerful Discovery Telescope to make fresh observations of the comet as it zoomed away from the sun on Wednesday (Nov. 5). The comet recently became visible again after swinging around the far side of our star.

Comets develop an atmosphere, or coma, as they fly close to the sun. This cloud of gas and dust grows larger and brighter as the sun heats up ice and other materials on the comet, which sublimate into gases that astronomers can observe. In this case, the atmosphere is brightest when viewed with a green filter, like with most comets that fly close to our star.

Zhang used a filter to detect diatomic carbon (C₂) particles, which glow green. He noted that there's a bunch of large molecules in the comet that contain carbon and hydrogen (hydrocarbons). And when the comet gets close to the sun, ultraviolet (UV) light breaks these molecules apart.

"It's sort of for the same reason that if we stay out in the sun too long without sunscreen, we get sunburnt," Zhang told Live Science. "The UV rays are destroying our DNA [in our skin cells], which is kind of a similar type of molecule in the sense that it's big and contains carbon."

When this happens on a comet, some of the molecule chunks are two carbon atoms stuck together, or diatomic carbon, which are easy for astronomers to detect.

The comet appears to lack a dust tail in the image, but it's still there. Zhang noted that if you look closely at the image, you can see it's a bit brighter on the left side of the comet than on the right. That slight asymmetric glow occurs because we're seeing the tail basically head-on, and it's right behind the comet, curving slightly off to the left. In other words, the comet's apparent lack of tail isn't anything to get excited about.

Comet 3I/ATLAS has become a celestial celebrity since its discovery in July. A lot of this buzz stems from speculation that the comet might be an alien spacecraft, even though most astronomers are confident that the interstellar visitor is a comet from an unknown star system in the Milky Way.

However, describing 3I/ATLAS as just a regular comet would do this rare solar system interloper an injustice. The comet is only the third interstellar visitor ever recorded and could be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than the solar system.

Comet 3I/ATLAS has only recently become visible from Earth again after it briefly disappeared behind the sun, reaching its closest point to our star, known as perihelion, on Oct. 29. This post-perihelion phase opens up a critical window for astronomers hoping to learn more about the comet's gases and makeup, as comets tend to be their most active at perihelion.

Preliminary research suggested that prolonged exposure to space radiation has given comet 3I/ATLAS a thick irradiated crust that no longer resembles its home star system. If confirmed, this crust could mean scientists will have a harder time deciphering 3I/ATLAS' origins, as it will be venting irradiated material rather than pristine material from its home star system.

Zhang previously used the Lowell Discovery Telescope to get a first optical, post-perihelion look at 3I/ATLAS from Earth on Halloween (Oct. 31). As with his first observation, the new sighting was made during morning twilight. The comet is moving northward from our perspective, away from the northeastern horizon. At the moment, it's possible to observe the comet early in the morning, when the comet is rising above the horizon.

Zhang took multiple images of the comet with different filters. The diatomic carbon image, which he first posted to his Cometary blog on Wednesday, roughly depicts what the comet might look like if humans were able to see it with the naked eye.

On Oct. 28, Zhang and his colleague posted a study to the preprint server arXiv that suggested comet 3I/ATLAS underwent rapid brightening ahead of perihelion and was distinctly bluer than the sun. The green in the new image doesn't mean that the comet changed color after perihelion — it might have changed color before.

Zhang noted that, in astronomical terms, bluer or redder typically refers to longer (red) or shorter (blue) wavelengths of light, with the new observation matching the latter. The comet is a lot brighter when viewed with bluer filters than redder filters, though the bluer filters are more of a mix of green and blue, and not actually that sensitive to pure blue.

"It's brightest in the bluest filter that we have," Zhang said.

The Lowell Discovery Telescope was likely one of the largest telescopes that could point close enough to the horizon to see comet 3I/ATLAS immediately after perihelion, according to Zhang. However, he noted that the comet is now high enough above the horizon that a number of large telescopes can make observations — small personal telescopes with a 6-inch (15 centimeters) lens can also spot it.

Expect a flurry of interesting findings on the comet in the coming months.

Interstellar comet 3I/ATLAS may be developing a blueish hue after undergoing a rapid and unexpected brightening event while hidden behind the sun, new observations reveal. This is the third time that experts have noted a potential change to the comet's color — but, so far, none of them have stuck.

3I/ATLAS, the third-known interstellar object to visit our solar system, was spotted shooting toward the sun at more than 130,000 mph (210,000 km/h) in early July. The comet is potentially the oldest of its kind ever seen and was likely ejected from its home star system, somewhere in the Milky Way's frontier, more than 7 billion years ago. Since then, it has sailed through interstellar space, before making its current rendezvous with our solar system.

Following a close approach to Mars at the start of October, the interstellar comet has spent the last few weeks on the opposite side of the sun to Earth, making it largely unobservable from our planet (although a handful of orbiting spacecraft could still see it). But it is now starting to become visible to Earth-based telescopes once again.

The comet reached its closest point to the sun, known as perihelion, on Oct. 29, when it was mostly hidden from us, reaching a minimum distance of 130 million miles (210 million kilometers) from our home star — around 1.4 times farther from the sun than Earth. The day before, a pair of researchers analyzing data from spacecraft that could still see 3I/ATLAS revealed that the comet had brightened by several orders of magnitude after disappearing from view, which can't be fully explained by its proximity to the sun.

In the same paper, the researchers also wrote that the comet appears to be "distinctly bluer than the sun," which came as a surprise given that this color had not been seen in the comet until now. This color change is likely the result of a specific gas, such as carbon monoxide or ammonia, leaking from the comet, they argued. (This study has not yet been peer-reviewed, and no other observations have thus far confirmed the blue coloration.)

The researchers noted that the blue coloration is in sharp contrast to the initial red hue given off by the comet during early observations in July, which was likely the result of an abundance of dust coming off its surface. Then, in September, the comet briefly appeared to be turning green, likely due to the presence of dicarbon or cyanide within its coma.

But these changes of coloration were only temporary, and it's currently unclear why that is. Only time and continued observations will tell if the comet's new coloring will stick.

Over the next few weeks, the comet will become increasingly visible to stargazers in the Northern Hemisphere as it moves northward in the night sky. However, it will not be visible to the naked eye, meaning you will need a decent telescope or a pair of stargazing binoculars to see it for yourself.

3I/ATLAS will reach its closest point to our planet on Dec. 19, coming within a minimum distance of 168 million miles (270 million km) — around 1.8 times the Earth-sun distance. Between now and then, researchers will get a much better look at the comet, enabling them to study it in even greater detail. Two ESA spacecraft may also fly through the comet's long tail before it begins its journey back out of the solar system.

The extrasolar entity has displayed several unusual traits since it was first discovered, including an abundance of carbon dioxide, high levels of water leakage and a puzzling anti-tail. Researchers also believe that its icy shell may have been transformed by billions of years of cosmic ray bombardment, potentially making it harder to track the material of its home star system.

As a result of these anomalous characteristics, some researchers have controversially proposed that 3I/ATLAS may be a piece of alien technology in disguise. However, there is no solid evidence to support this theory, and most experts maintain that the object is behaving exactly as a comet should.

The interstellar comet 3I/ATLAS has become visible from Earth once again after zooming behind the sun, new images reveal.

An astronomer used the Lowell Observatory's powerful Discovery Telescope in Arizona to snap what is believed to be the first optical post-perihelion shot of the interstellar visitor on Halloween, Friday (Oct. 31).

Qicheng Zhang, a postdoctoral fellow at the observatory, has subsequently found that the comet is also visible using small telescopes, posting an example of this to his Cometary blog on Sunday (Nov. 2). According to Zhang, standard amateur telescopes should now start picking up the comet across much of the Northern Hemisphere.

"All you need is a clear sky and a very low eastern horizon," Zhang told Live Science on Friday. "It won't look very impressive, it's just a smudge, but it will be an increasingly visible smudge over the next few days."

Scientists have learned a lot about comet 3I/ATLAS since its discovery in July. The comet, which is only the third interstellar object ever recorded, appears to be zooming through our solar system at speeds in excess of 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory.

The comet briefly disappeared from Earth's view as it slingshotted around the sun, reaching its closest point to our star, known as perihelion, on Thursday (Oct. 29) — it came within 1.4 astronomical units, or 130 million miles (210 million kilometers) of the sun. But researchers and amateur astronomers used data from space telescopes to continue following the comet's path even after it was obscured by the sun.

On Oct. 28, Zhang and his colleague posted a study to the preprint server arXiv that suggested comet 3I/ATLAS underwent rapid brightening ahead of perihelion and was distinctly bluer than the sun, which was consistent with gas emissions contributing a substantial fraction of the visible brightness near perihelion. Zhang noted that the comet could still be brightening, but more data is needed to say one way or the other.

The Lowell Discovery Telescope is likely one of the largest telescopes that can point close enough to the horizon to see comet 3I/ATLAS so soon after perihelion, according to Zhang. The comet is moving northward from our perspective, away from the northeastern horizon. Zhang noted that there's a window to observe the comet in the morning twilight, when the comet is just above the horizon but the sun is still far enough below it that the sky isn't too bright.

Time is a precious resource for large telescopes, so Zhang uses a small telescope (6-inch lens) to experiment and learn about what conditions to expect ahead of his scheduled windows on the Lowell Discovery Telescope. He successfully captured the new image when the comet was about 16 degrees away from the sun (5 degrees above the horizon).

Zhang noted that there have been radio observations of comet 3I/ATLAS throughout its perihelion, and it's possible someone else made an optical post-perihelion observation before him, but he hasn't seen any others.

We're entering an important period for observations of 3I/ATLAS. Comets heat up as they fly closer to stars, which causes ice on their surface to sublimate into gas. This means that researchers should be able to learn more about the comet's makeup as it flies away from our star.

There has been some frenzied speculation in the media that 3I/ATLAS might be an alien spacecraft, but most astronomers are confident that this interstellar visitor is a regular comet from an unknown star system in the Milky Way. Comet 3I/ATLAS could also be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than the solar system.

Some preliminary research has suggested that prolonged exposure to space radiation has transformed the interstellar traveler, giving it a thick irradiated crust that no longer resembles its home star system. If that's the case, scientists will have a harder time deciphering the comet's origins. Regardless, we can expect a flurry of new comet 3I/ATLAS research in the coming months as it reappears in the night sky.

"The comet is rapidly rising from the sun," Zhang said. "I think in one week it's going to be something like 25 or 30 degrees away from the sun, by which point there will be a large number of other big telescopes around the world that will also be able to start to follow it up."

Comet 3I/ATLAS is extremely irradiated from billions of years of cosmic ray bombardments, new research using observations from the James Webb Space Telescope (JWST) has revealed.

The comet has soaked up so many galactic cosmic rays during its interstellar journey through the Milky Way that it has developed a deep irradiated crust that no longer resembles the material of its home star system, the new research hints.

Using JWST observations and computer simulations, researchers have determined that the comet's previously documented "extreme" levels of carbon dioxide (CO₂) enrichment are from space radiation absorbed over its estimated 7-billion-year lifespan, according to the study posted to the preprint server arXiv on Friday (Oct. 31). The findings have not yet been peer reviewed.

Galactic cosmic rays — a kind of space radiation made up of high-energy particles from outside of the solar system — strike carbon monoxide (CO) in space to convert it to carbon dioxide (CO₂). In our solar system, the heliosphere — the enormous bubble of radiation emitted by the sun — shields Earth and its neighbors from a majority of this cosmic radiation. But in interstellar space, where 3I/ATLAS has spent most of its life, no such protection exists.

The authors of the new study concluded that over billions of years, cosmic rays have significantly altered the physical state of comet 3I/ATLAS' ice, down to a depth of about 50 to 65 feet (15 to 20 meters).

"It's very slow, but over billions of years, it's a very strong effect," study lead author Romain Maggiolo, a research scientist at the Royal Belgian Institute for Space Aeronomy, told Live Science.

The findings, which the researchers described as a "paradigm shift" for studying interstellar objects, suggest that objects like comet 3I/ATLAS are primarily made up of galactic cosmic ray-processed material rather than pristine material that is representative of the environments in which they formed.

In other words, comet 3I/ATLAS is now a product of its interstellar journey rather than where it came from — at least on the outside.

Tracking the interstellar visitor

Comet 3I/ATLAS is currently flying around the sun. The comet reached perihelion (its closest point to our star) on Thursday (Oct. 29). Comets heat up as they draw closer to stars, causing ices on their surface to sublimate into gas. The new findings suggest that before perihelion, any gases ejected from the comet were merely from its irradiated outer shell. This is likely to continue post-perihelion, but Maggiolo noted that while it's unlikely, solar erosion might be strong enough to expose the pristine materials from the comet’s home star that are locked away in its nucleus.

"It will be very interesting to compare observations before perihelion, so the first observation we had when it arrived in the solar system, with observations made after perihelion when there was some erosion," Maggiolo said. "Maybe by looking at these differences, we can have some indication about its initial composition."

Since its discovery in July, researchers have been using various telescopes to learn all they can about 3I/ATLAS. Their findings so far indicate that the comet is zooming through our solar system at speeds in excess of 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory. 3I/ATLAS could also be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than our 4.6 billion-year-old solar system.

The new research builds on a previous work that documented comet 3I/ATLAS is rich in CO₂, based on JWST's first images of the interstellar visitor in August, and observations from NASA's SPHEREx orbiter, also made in August.

Maggiolo and his colleagues had been studying the irradiation of a domestic comet (comet 67P), which passes between the orbits of Jupiter and Earth, and adapted their models from a 2020 study published in The Astrophysical Journal Letters to apply to comet 3I/ATLAS.

The team modeled the cumulative effects of galactic cosmic ray exposure on both ice structure and chemical composition after 1 billion years of irradiation. The method relies on laboratory experiments that simulated the effects of galactic cosmic rays, and thus might not be completely representative of interstellar conditions. Nonetheless, the tests offer a robust indicator of what comets experience on their lonely, multibillion-year journeys through interstellar space, according to the study.

The simulations found that 1 billion years of irradiation was sufficient for comet 3I/ATLAS to form its deep irradiated crust. Maggiolo noted that comet 3I/ATLAS is still full of interesting information, but it has aged and changed, which researchers will need to take into account during their analyses.

"We have to be careful and take into account aging processes, so it's more work for scientists, but [3I/ATLAS] remains very interesting," Maggiolo said.

3I/ATLAS is the third interstellar object ever discovered in our solar system. Telescope observations suggest it is a roughly 7-mile-wide (11 kilometers) comet zooming at more than 130,000 mph (210,000 km/h). Astronomers discovered it in early July as it emerged from beyond the orbit of Jupiter. An analysis of the comet’s composition and unusually flat, straight trajectory revealed that it did not originate within our cosmic neighborhood, and was likely ejected from a distant star system long before our sun ever formed.

The exotic comet has many peculiar properties, from its chemical composition to its large size. This has fuelled speculation that the comet is an alien spacecraft intentionally guided here. That’s almost certainly not the case, but it doesn’t mean that astronomers aren’t excited about studying it to better understand the conditions around other stars, the early Milky Way, and the frontier of interstellar space.

3I/ATLAS reached its closest point to Earth on Friday (Dec. 19) and is now zooming away forever. Research continues to pour in as telescopes around the solar system observe the strange comet's passage.

Comet 3I/ATLAS is rapidly brightening as it swings behind the sun, spacecraft observations have revealed.

The comet has been flying around the sun, obscuring it from Earth’s view, to reach perihelion (its closest point to our star) on Thursday (Oct. 29).

Yet, while most of the world has been waiting for it to re-emerge, some researchers and amateur astronomers have been using spacecraft to follow its path.

On Oct. 18, amateur astronomer and seasoned comet hunter Worachate Boonplod spotted the comet in images from the National Oceanic and Atmospheric Administration's GOES-19 weather satellite, which uses an instrument called CCOR-1 to observe the sun as part of its regular space weather monitoring. Boonplod noted that comet 3I/ATLAS was easily detectable and was set to remain visible to the spacecraft until Oct. 24.

"Its brightness is comparable to nearby stars with magnitude ~11," Boonplod wrote on the Comets Mailing List group, part of the group email service Groups.io. (In astronomy, a higher magnitude corresponds to a brighter object; typically, objects with a magnitude greater than 6 are too faint for the naked eye to see.) "The comet is moving from left to right (relative to both the field and background stars) and should go out of the CCOR-1 field on October 24."

The GOES-19 satellite wasn't the only satellite with comet 3I/ATLAS in its sights. Also tracking it are NASA's Polarimeter to Unify the Corona Heliosphere (PUNCH) mission, which includes four small satellites aimed at the sun, as well as NASA and the European Space Agency's Solar and Heliospheric Observatory (SOHO), Universe Today reported. SOHO orbits the sun at almost 1 million miles (1.5 million kilometers) from Earth, with its Large Angle and Spectrometric Coronagraph (LASCO C3) instrument keeping track of comet 3I/ATLAS until Oct. 26. Coronagraphs, like those used by SOHO and GOES-19, are instruments that intentionally block the sun in images in order to study the surrounding atmosphere, or corona.

On Wednesday (Oct. 28), two researchers posted a study to the preprint server arXiv that reported comet 3I/ATLAS underwent rapid brightening ahead of perihelion. The team estimates that, at perihelion, the comet will have brightened to roughly magnitude 9 — still too faint to be seen with the unaided eye, but bright enough to be seen by good backyard telescopes, if it were visible from Earth.

The study relied on space-based solar instruments like GOES-19 and SOHO, and found that the comet was distinctly bluer than the sun, which was consistent with gas emissions contributing substantially to the comet’s increased brightness near perihelion, according to the study's authors. This is expected of comets, which heat up as they approach the sun, causing surface ices to sublimate into gases that wrap around the comet’s body and contribute to its tail. Solar radiation ionizes the gas, causing further brightening.

Scientists have been using various telescopes to learn all they can about comet 3I/ATLAS since its discovery in July. The comet is only the third interstellar comet ever recorded, and findings thus far indicate that it's zooming through our solar system at speeds in excess of 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory.

Despite some rather frenzied speculation that comet 3I/ATLAS could be an alien spacecraft, most astronomers are confident that this interstellar visitor is a space rock from an unknown star system far away.

The speed of the comet, which has the highest velocity ever recorded for a solar system object, suggests that it has been traveling for billions of years, gaining momentum from a gravitational slingshot effect as it whips by stars and nebulas, according to a NASA statement .

In fact, 3I/ATLAS could be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than our 4.6 billion-year-old solar system. The comet is also likely the largest interstellar object ever seen, though researchers are still pinning down its exact size. Hubble Space Telescope data suggest that 3I/ATLAS has a maximum width of about 3.5 miles (5.6 km).

The comet will become visible again to Earth-based telescopes by early December, according to NASA, and may even be visible to spacecraft orbiting Jupiter as it makes a close approach to the gas giant in March, 2026.

Even as a brilliant, naked-eye comet slices through Earth's sky (cheers, Comet Lemmon!), the most famous object in the solar system right now is hidden on the far side of the sun: the interstellar comet 3I/ATLAS.

This alien visitor, which most astronomers believe to be a comet originating from an unknown star system far beyond our own, is only the third interstellar object ever detected in our solar system. It is the largest, fastest-moving, and quite likely the oldest interstellar object ever seen.

Though it was just confirmed by NASA in early July, the freewheeling ball of ice and dust is already nearing the halfway point on its tour of our solar system. This Wednesday (Oct. 29), 3I/ATLAS will reach perihelion — its closest point to the sun — before beginning its months-long departure from our cosmic neighborhood.

We'll miss our interstellar friend, but at least we'll always have the photos. The image above, captured Aug. 27 by the National Science Foundation-operated Gemini South telescope in Chile, may be the clearest image we have so far. As 3I/ATLAS zooms closer to the sun, radiation from our star heats the ice on the comet's body (its nucleus), causing geysers of gas and dust to shoot outward and form a glowing plume (a coma) around it. Radiation pressure from our star's unrelenting solar wind pushes this material into a long, prominent tail angled away from the sun.

As 3I/ATLAS reaches perihelion this week — coming within 1.4 astronomical units, or 130 million miles (210 million kilometers) of the sun, according to NASA — it may start releasing gas in overdrive. When the comet becomes visible to telescopes again in early November, it may look both bigger and brighter than how it appeared two months ago. Instruments on the ground, in orbit and even on their way to Jupiter will snap to attention, making 3I/ATLAS an even bigger space celebrity as it zooms away from our solar system forever.

Studying the interstellar comet with the full range of humankind's astronomical instruments could yield untold secrets about the outer reaches of our galaxy and its mysterious history. Until then, all we can do is wait, feel the warm sunlight on our faces, and know that a trove of cosmic information lurks just on the other side of our star.

For more sublime space images, check out our Space Photo of the Week archives.

All sorts of crazy things have been suggested regarding 3I/ATLAS, the third known interstellar object that we've discovered. Some are simply conspiracy theories about it being an alien spacecraft, while others have been well-thought out suggestions, like using Martian-based probes to observe the comet as it streaked past the red planet.

A new paper pre-published on arXiv and accepted for publication by the Research Notes of the American Astronomical Society by Samuel Grand and Geraint Jones, of the Finnish Meteorological Institute and ESA respectively, falls into the latter category, and suggests utilizing two spacecraft already en route to their separate destinations to potentially detect ions from the object's spectacular tail that has formed as it approaches the Sun.

Those two spacecraft are Hera and Europa Clipper - both of which are on their way to missions in drastically different parts of the solar system. Hera is on its way to Didymos-Dimorphos, the binary asteroid that was impacted by the DART mission in 2022. Europa Clipper, as its name suggests, is on its way to Europa, one of Jupiter's four Galilean moons, intending to study its ice.

But, as luck would have it, both spacecraft are going to pass "downwind" of 3I/IATLAS in the next two weeks. Hera will have a window between October 25th and November 1st, whereas Europa Clipper will have a window between October 30th and November 6th.

A few weeks isn't a whole lot of time to set up a rapid experiment to run a test that neither spacecraft were designed for. But sometimes science means doing the best with what you have, and in this case, these two spacecraft are our best bet to study the tail of an interstellar comet.

That tail has been consistently growing since the comet's discovery in early June. Recent reports of its "gushing" water indicate how massive the tail has become, leaving a wake of water particles, but potentially more importantly, ions, behind it. The comet also recently moved out of view from Earth-based systems, though assumedly its tail will continue to grow until it reaches perihelion on October 29th.

As the paper explains, ending up in part of its tail isn't as simple as passing directly behind it as it moves through the solar system - the solar wind pushes the particles out farther from the Sun, following a curved path away from the comet. The speed at which the wind hits those particles plays a major role in where they would be, and therefore where exactly the spacecraft would have to pass through to collect data on the tail directly.

To make those estimates, the authors used a model called "Tailcatcher" that estimates where the path of the cometary ions will go based on different wind speeds. It then calculated the "minimum miss distance" for a given spacecraft for the central axis of the comet's tail. Unfortunately, the model is only as accurate as the solar wind data, which typically is only collected definitively ex post facto - and certainly not enough time to help with this potential mission objective.

Even with the best estimates of the program, the two spacecraft would be millions of km away from the central axis - around 8.2 million for Hera and 8 million for Europa Clipper. However, that is still within range of being able to collect data on the ions from the tail directly as they can spread over millions of kilometers from very active comets like 3I/ATLAS.

The downside of this plan is that at least one of the spacecraft - Hera - doesn't have any instruments that could potentially detect either the ions expected in the tail, nor the magnetic "draping structure" that characterizes what the comet's atmosphere does to the magnetic field carried by the solar wind. However, Europa Clipper does - it's plasma instrument and magnetometer are exactly what would be needed to directly detect those ions and magnetic field changes.

Acting on this bit of serendipity is difficult to say the least - but it's also very time constrained. It's unclear whether the mission controllers for Hera, or perhaps more importantly, Europa Clipper, will see the message in time to do anything about their potential journey through the coma. But if they do, they might be the first in human history to directly sample and interstellar comet's tail - and wouldn't that be something to brag about that had nothing to do with their original intended mission?

The original version of this article was published on Universe Today.

Newly released images of the interstellar comet 3I/ATLAS appear to show the alien object spitting out an enormous jet of gas and dust toward the sun — just as comets are expected to do.

Discovered in late June and confirmed by NASA in early July, the comet originates from an unknown star system far beyond our own. 3I/ATLAS is only the third interstellar object ever detected. At somewhere between 3 and 7 miles (5 to 11 kilometers) wide, it is the largest interstellar object ever to cross our path, and likely the oldest, potentially dating to billions of years before the birth of the sun.

These and other peculiarities have led a small group of researchers to controversially claim that the object may be an alien spacecraft sent to spy on us. However, the vast majority of scientists maintain that 3I/ATLAS is a high-speed comet behaving exactly as comets should. The new images of the interstellar interloper, captured Aug. 2 by the Two-meter Twin Telescope (TTT) at the Teide Observatory in Spain's Canary Islands, further cement the object's natural origins.

Combining 159 exposures lasting 50 seconds each, the composite image shows the icy body (or nucleus) of 3I/ATLAS as a big, black dot, surrounded by a white glow. A sudden, fan-shaped break in this glowing ring shows where researchers say a large, high-speed jet of material (marked in purple) is blasting off of the comet in the direction of the sun. The image was shared to the transient object monitoring site The Astronomer's Telegram on Oct. 15 but has not yet been published in a peer-reviewed study.

Comets are famous for their glowing tails of ionized gas, the largest of which can stretch for hundreds of millions of miles in the opposite direction of the sun. Comet jets, by comparison, are much smaller and can point toward the sun. While a cannon of dust aimed at our star might sound suspicious, it's just a standard part of a comet's anatomy, Miquel Serra-Ricart, an astrophysicist and chief science officer at the Teide Observatory's Light Bridges research institution, told Live Science in an email.

"This is the usual," Serra-Ricart, who posted the new images, told Live Science. "Jets are pointing to [the] sunward direction and [the] comet's tail in the anti-solar direction."

This is because comets inevitably heat up as they swoop closer to the sun — but they don't always heat evenly. The sun-facing side of the comet heats up the fastest, and if a particular weak spot on the comet's surface warms up enough, a growing supply of sublimated gases can blast out like a geyser, shooting cometary material thousands of miles toward the sun.

As the comet's nucleus rotates, the jet can take on a fan shape akin to what we see in the new TTT image, Serra-Ricart added. The famous naked-eye comet NEOWISE also developed fan-like jets after its close flyby of the sun in 2020, Hubble Space Telescope observations showed at the time.

Some of that jet material ends up in the comet's coma (the glowing plume of material that surrounds the nucleus), while some may be forced into the comet's tail by radiation pressure from the onslaught of incoming solar wind. This is why comets can sport both a sun-facing jet and an anti-sunward tail at the same time — no alien technology required.

It's unclear how far this newly discovered jet extends at the moment, but Serra-Ricart estimated that it could stretch roughly 6,200 miles (10,000 km) from 3I/ATLAS' surface. The jet is likely composed largely of dust particles and carbon dioxide, he added, which is consistent with the makeup of the large gassy plume that the James Webb Space Telescope detected around the comet in August.

3I/ATLAS swooped past Mars on Oct. 3 and is currently approaching its closest point to the sun (perihelion), which it will reach on Oct. 29. The comet is on the far side of the sun now and won't be visible from Earth again until mid-November. When it reemerges, astronomers will get a rare chance to see how the mysterious visitor changed after its date with the sun and to what extent its jet and tail may have grown.

The interstellar comet 3I/ATLAS began blasting water "like a fire hose" before it was anywhere near the sun, according to a recent study.

Researchers observed the comet scattering water unusually early in a discovery that sheds light on how the building blocks of life are distributed across other planetary systems.

Initial James Webb Space Telescope observations have suggested that 3I/ATLAS has a high carbon dioxide (CO2) to water (H2O) ratio. In the new study, published Sep. 30 in The Astrophysical Journal Letters, researchers explored water activity on the comet and provided the first clear evidence that it was shedding water while still remarkably far from the sun.

"When we detect water — or even its faint ultraviolet echo, OH — from an interstellar comet, we're reading a note from another planetary system," study co-author Dennis Bodewits, a professor of physics at Auburn University in Alabama, said in a statement. "It tells us that the ingredients for life's chemistry are not unique to our own."

NASA's Neil Gehrels Swift space observatory detected hydroxyl (OH) gas, an ultraviolet by-product of water, coming off the comet when it was nearly three times farther from the sun than Earth (2.9 astronomical units away), much farther away than the region of our solar system where water ice typically turns to gas on passing comets.

Researchers calculated that the comet was shedding about 88 pounds (40 kilograms) of water per second, which is about the equivalent of a fire hose running at full blast, according to the statement released by the researchers.

Since its discovery in July, scientists have been using various telescopes to learn all they can about 3I/ATLAS. Their findings so far indicate that the comet is zooming through our solar system at speeds in excess of 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory.

3I/ATLAS is likely the largest interstellar object ever seen, though researchers are still pinning down its exact size. Hubble Space Telescope data suggest that 3I/ATLAS has a maximum width of about 3.5 miles (5.6 km). 3I/ATLAS could also be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than our 4.6 billion-year-old solar system.

For the new study, researchers used observations made with the Neil Gehrels Swift Observatory's ultraviolet and optical telescope in July and August. The researchers suggested that the ultraviolet hydroxyl signal could be the result of sunlight heating small icy grains on the nucleus (head) of the comet, causing them to vaporize into gas.

3I/ATLAS is only the third interstellar comet ever recorded, following the discovery of the cigar-shaped 1I/'Oumuamua comet in 2017 and the pristine 2I/Borisov comet in 2019. So far, each interstellar visitor has had some differing characteristics, suggesting that there could be a variety of comet and planet-forming environments in the universe.

"Every interstellar comet so far has been a surprise," study lead author Zexi Xing, a postdoctoral researcher at Auburn University, said in the statement. "Oumuamua was dry, Borisov was rich in carbon monoxide, and now ATLAS is giving up water at a distance where we didn't expect it. Each one is rewriting what we thought we knew about how planets and comets form around stars."

Two spacecraft on Mars have captured new images of the interstellar comet 3I/ATLAS in the closest view that the European Space Agency (ESA) will get of the mysterious object, according to an ESA statement.

The comet, which came from an unknown star system far beyond our own, is currently taking a months-long tour of the inner solar system. It made its closest approach to Mars Friday (Oct. 3) ahead of a close encounter with the sun on Oct. 30. During its recent flyby of the Red Planet, the comet came within view of ESA and NASA's fleet of robotic explorers, including ESA's ExoMars Trace Gas Orbiter (TGO) and Mars Express orbiter.

Soaring 18.6 million miles (30 million kilometers) overhead, the comet proved too dim for Mars Express to capture. However, the ExoMars TGO satellite succeeded in snapping a series of images, which ESA combined into an animated GIF. The animation shows the comet — visible as a fuzzy, bright dot — descending toward the center of the frame as it zooms away from Mars at an estimated 130,000 mph (210,000 km/h).

What can we see?

The bright dot represents the comet's nucleus (the ball of icy rock that makes up the body of the comet) and its coma (the nebulous cloud of gas that streams off the nucleus as it heats up). As comets swoop closer to the sun, ice on their surfaces sublimates into gas, causing the coma to grow larger and brighter, according to NASA. Pressure from incoming solar wind can also blow the coma's gas and dust away from the sun, giving comets their distinctive tails.

Because TGO was designed to monitor the Martian surface from just a few hundred miles away, its instruments aren't the best at recording faraway, fast-moving objects like 3I/ATLAS, ESA officials noted.

"The comet is around 10,000 to 100,000 times fainter than our usual target," Nick Thomas, principal investigator for ExoMars' Colour and Stereo Surface Imaging System, said in the statement. As a result, no tail is visible in the new images. But that doesn't mean the comet doesn't have one; as 3I/ATLAS careens closer to the sun, both its coma and its tail are likely to grow and brighten, ESA officials added.

At the moment, the new images don't reveal any new insights about the peculiar object, but ESA will continue to analyze images from both of its Mars satellites in hopes of teasing out some new data on the comet's possible size and composition.

It remains uncertain whether any of NASA's dedicated Mars rovers or satellites also spotted the comet during its close approach, as the agency has paused all public communications during the ongoing U.S. government shutdown. However, a raw image captured by the Perseverance rover's Right Navigation Camera on Oct. 4 shows a bright, streaking object in the sky that may be Comet 3I/ATLAS, according to Live Science’s sister site Space.com. No official information about the image has been released.

3I/ATLAS is the third interstellar object ever confirmed — after 1I/'Oumuamua and 2I/Borisov — and appears to be the largest so far, with estimates placing it somewhere between 3 and 7 miles (5 to 11 km) wide. Its speed and trajectory suggest that it has been zooming through the galaxy for billions of years and is likely far older than the sun.

The comet is currently traveling on the far side of the sun, out of Earth's view, but it will become visible to ground-based telescopes again in early December. The comet will whiz past Jupiter in March 2026, before heading out of our solar system forever.

Astronomers may be closing in on the age and origin of the interstellar comet 3I/ATLAS as it barrels toward the center of our solar system.

A new study that models the last 4 million years of the comet's journey through the Milky Way hints that the interstellar visitor came from far, far away — potentially originating from the wild frontier where the galaxy's oldest and youngest stars meet. If that's the case, the comet may be a relic of the early galaxy, dating billions of years older than Earth's sun.

First spotted in late June and confirmed by NASA in early July, 3I/ATLAS is a peculiar comet whose staggering speed and odd trajectory indicate that it came from a star system beyond our own. It is only the third interstellar object ever detected — after 1I/'Oumuamua and 2I/Borisov — and appears to be the largest so far, with recent estimates putting it somewhere between 3 and 7 miles (4.8 to 11.2 kilometers) wide.

Galactic grand tour

This cosmic visitor is currently taking a months-long sightseeing tour through our inner solar system, completing a close approach to Mars on Friday (Oct. 3) and poised to make its closest swoop past the sun on Oct. 30, according to NASA. After that, it will head out toward interstellar space again, passing Jupiter in March of 2026 before finally disappearing from view. The comet poses no threat to Earth.

While 3I/ATLAS's immediate trajectory is easy to predict, figuring out where it came from is much harder.

Traveling at about 130,000 miles per hour (210,000 kmh), a record for interstellar objects, the renegade ice ball has been picking up speed for millions, if not billions, of years. That leaves it vulnerable to the gravitational tugs of an untold number of Milky Way stars. Just as NASA uses the gravitational influence of our solar system's planets to slingshot spacecraft into deeper orbits, 3I/ATLAS could easily have been knocked off its original trajectory by the gravity of massive stars intervening in its path.

Now, new research published to the preprint server arXiv makes the best effort yet to pin down the comet's origins by looking at which nearby stars, if any, may have influenced its orbit.

Using data from the European Space Agency's now-retired Gaia space telescope, the study authors traced the comet's trajectory back in time 4.27 million years and identified 62 nearby stars that the interstellar object likely encountered along the way. Using Gaia's high-definition data on the stars' motions, velocities and sizes, the study authors concluded that none of them have significantly altered the comet's orbit — hinting that it did not originate anywhere near us.

"We have found that none of the stars in the solar neighborhood can explain the trajectory and high velocity of 3I/ATLAS," lead study author Xabier Pérez-Couto, an astrophysics postgraduate student at Spain's Universidade da Coruña, told Live Science in an email. Only one nearby star, measuring about 70% the mass of the sun, appears to have impacted the comet's trajectory at all, but it was only by a negligible amount, the researchers added in their paper.

This led the team to postulate that "3I/ATLAS is a very old object, that has been traveling for [billions of years], and that its origin belongs to the border of the thin disk," Pérez-Couto said.

Object from the wild frontier?

What's so special about that? Spiral galaxies like the Milky Way divide their stars between a thin disk and a thick disk. Slicing through the central bulge of our galaxy, the younger and smaller thin disk is thought to contain the vast majority of the Milky Way's stars and star-forming gases — most of which are rich in elements heavier than hydrogen and helium, picked up from the older generations of stars that lived and died before them. By contrast the broader thick disk, wrapped around the borders of the thin disk, has long ceased its star formation. It contains a smaller — but much older — sampling of stars that are poor in heavy metals, according to Swinburne University of Technology in Australia.

If comet 3I/ATLAS did indeed originate from the border of these two disks, it could mean the object is incredibly old — potentially 10 billion years old, making it more than double the age of our roughly 4 billion-year-old sun. According to Pérez-Couto, the comet was likely "ejected from the primordial disk of an early formed planetary system," potentially making it a valuable time capsule of the ancient Milky Way.

However, the new study acknowledges the limitations of its approach: by looking at nearby stars, the analysis only accounts for a few million years of the comet's long history, making its exact origin still highly uncertain. As 3I/ATLAS continues to zoom through the solar system, scientific instruments on Earth and Mars, as well as those in orbit around Jupiter, will soon have the chance to study it in much greater detail. Unraveling the interstellar object's composition will provide essential clues to its cosmic birthplace — and potentially open a precious window into our galaxy's past.

Surprising new photos of comet 3I/ATLAS taken during last week's total lunar eclipse hint that the "interstellar visitor" may be turning bright green as it approaches the halfway point on its journey through the solar system. This unexpected transformation, if confirmed, is likely the result of the comet's increasing proximity to the sun, experts say.

3I/ATLAS is a roughly 7-mile-wide (11 kilometers) comet that was first spotted in early July, zooming toward us at more than 130,000 mph (210,000 km/h) from beyond the orbit of Jupiter. Astronomers quickly realized that the superfast object did not originate within our cosmic neighborhood, and was instead passing through on a one-way trip. It was likely ejected from a distant star system within the Milky Way and is probably much older than the solar system.

The comet is now closing in on a flyby of Mars next month, before reaching its minimum distance from the sun on Oct. 29. As the interstellar interloper gets closer to the sun, it has started to soak up more solar radiation, causing more ice, gas and dust to be expelled from its core, which has allowed it to start growing a traditional cometary tail.

But on Sept. 7, astrophotographers Michael Jäger and Gerald Rhemann snapped new shots of the comet in the dark skies over Namibia. These images were taken during the "blood moon" total lunar eclipse, when the full moon passed through the darkest part of Earth's shadow, meaning that the skies were darker than normal for that time of month. The resulting photos show 3I/ATLAS with a surprising emerald hue.

The new images suggest that the comet's increasing proximity to the sun has caused it to "turn green" as new rarer chemicals are expelled from its core, Spaceweather.com reported. However, it is still too soon to tell for sure, as no other photographers or observatories have so far witnessed this change.

Related: Here we go again! Controversial paper questions whether interstellar visitor 3I/ATLAS is 'possibly hostile' alien tech in disguise

This is not the first time that astronomers have spotted a green glow coming from a comet. In recent years, there have been several other emerald ice balls, including the aptly nicknamed "green comet" C/2022 E3, which passed by us in early 2023. The explosive "devil comet" 12P/Pons-Brooks also turned green as it neared the sun in 2024, while astronomers spotted another green comet, named SWAN25F, earlier this year.

The most common cause of this rare coloring is the presence of "dicarbon" in the clouds of ice and gas that surround comets, known as their comas. This molecule, also called diatomic carbon, is a form of carbon where two atoms are bonded together. Normally, pure carbon exists as solitary, unbonded atoms or within larger structures, such as diamonds.

So far, spectroscopic observations of 3I/ATLAS have not detected dicarbon in the comet's coma. However, it is possible that the molecule was locked away beneath layers of ice that have since been melted away by solar radiation, Spaceweather.com representatives wrote. "Or the green glow might come from some other mix of gases or dust, mimicking a classic cometary color with unfamiliar chemistry," they added.

Avi Loeb, an astronomer at Harvard University who is renowned for studying interstellar objects for possible signs of alien technology, has another explanation. On his personal blog, he wrote that the color could be caused by cyanide, which was spotted in the comet's coma in late August by the Very Large Telescope in Chile's Atacama Desert.

As a result, more photos and observations will be needed in the coming weeks to confirm the new coloration and uncover what may be causing it.

Unfortunately, the comet will soon disappear from view as it passes the sun on the opposite side from Earth. It will reappear in a few months, shortly before reaching its closest point to Earth in December, when it will be around 700 times further away from us than the moon.

Few cosmic visitors have captured the fascination of astronomers quite like the interstellar comet 3I/ATLAS. Hurtling through our solar system from the depths of interstellar space, this icy wanderer is only the third known object of its kind, and where it came from remains a mystery.

Since its discovery on July 1, 2025, by the Deep Random Survey remote telescope in Chile, part of the ATLAS (Asteroid Terrestrial-impact Last Alert System) project, scientists have raced to point telescopes toward the visitor as experts and the public are eager for a closer look. Even NASA's Hubble Space Telescope and the James Webb Space Telescope recently caught glimpses of this icy comet as it continues moving toward our sun.

So, when I heard that the Gemini South Observatory in Chile was hosting a live webcast event   —   as part of the Shadow the Scientists (StS) initiative, which works to bring the public into the fold of real-time research   —   I knew I had to join. From the moment the livestream session began, I and other participants were thrown into the control room at Gemini South as astronomers began calibrating the telescope. The team planned to use the GMOS (Gemini Multi-Object Spectrographs) as well as the new Gemini High-resolution Optical SpecTrograph (GHOST) instrument to measure the chemical composition of 3I/ATLAS.

Astronomer Karen Meech from the Institute for Astronomy of the University of Hawai'i reminded the audience just how rare opportunities like this are: "Interstellar objects are building blocks of other solar systems that got kicked completely out of their home star just by chance passing through ours. Whenever you get one of these  —  and we've only had three  —  everyone wants to use as much telescope time as possible to see if they're similar or different to the bodies in our solar system."

Related: New photos of interstellar comet 3I/ATLAS reveal its tail growing before our eyes

Other experts added to Meech's point, saying that they had to ask the director of the Gemini South Observatory if they could take this specific time away from other observers in order to host the event. You can watch a recording of the event at the link below.

While Meech set the stage, the telescope team in Chile prepared the giant 26-foot (8-meter) mirror for its delicate work. Inside the control room, the science operations specialists gave us a window into the process: "We are taking calibrations, tuning the telescope and checking the sky conditions … Tonight it's very dry, with steady winds, perfect for good seeing."

The comet stuck with me, as it was only recently that the area had been dusted with snow. While the Gemini South Observatory wasn't as badly hit with precipitation, lower down, its neighbor, the Atacama Large Millimeter/submillimeter Array (ALMA) facility on the Chajnantor Plateau, had enough snow that it temporarily suspended all science operations. Thankfully, the snow had melted by the time of the live event, allowing for everything to proceed as smoothly as possible.

As the calibrations continued for an hour, Meech answered questions and hyped the audience up for when the comet could be spotted: "We just don't know what we're going to see tonight, and that's exciting."

Before Gemini South began looking, both Hubble and JWST had already taken an early look. Hubble estimated the comet's nucleus, or core, to be less than 1.86 miles (3 kilometers) across, buried under a halo of dust and gas. JWST, meanwhile, struggled to see the nucleus because of that halo, revealing that 3I/ATLAS seems to be unusually rich in carbon dioxide. That makes it different from its predecessor 2I/Borisov, the second interstellar comet ever detected, which had far more carbon monoxide.

Meech and the others at Gemini South hoped to see if they could confirm that 3I/ATLAS does in fact have lots of carbon dioxide, or dry ice, which would burn off as the comet got closer to the sun. Meech explained that the comet's closest approach to the sun will be in October, but it will be impossible to spot as the comet moves behind the sun at that time. She mentioned that NASA scientists are currently discussing whether existing spacecraft could be temporarily repurposed to observe 3I/ATLAS on the other side of the sun, removing this blind spot.

Even if this isn't the case, observations can resume in November when 3I/ATLAS re-emerges from behind the sun, and, depending on its activity and chemical composition, the comet could appear even brighter as it burns off more gas and dust. But even if 3I/ATLAS does indeed brighten up, the window for scientists to study it will still be limited.

"Once these objects get too faint to see, they will never be seen again," Meech said. "They are just passing through our solar system. Even 1I/'Oumuamua is still within our solar system. It is out in the vicinity of the Kuiper Belt now."

'Oumuamua is the first interstellar object ever spotted in our solar system. Astronomers detected it back in 2017.

As the telescope began turning toward 3I/ATLAS, a hush fell over the experts as everyone watched the shared screen of the scientists in the Gemini South control room. Meech had explained earlier that the first chemical they hoped to see using the GMOS was cyanide, as it interacts with sunlight.

Then came the first image, a bright, blurry smudge. There was a collective gasp as we all saw it, and the event chat was full of surprise and excitement.

"You're looking at a building block of someone else's home," Meech said. However, she added, "it's impossible to backtrack the comet based on its trajectory, as everything else is also moving around it."

The first images showed a faint but distant glow of a developing tail, confirmation that this visitor was behaving more like a "classic" comet than the odd, elongated ‘Oumuamua, which Meech had also studied.

"This is the raw image," she said. "I bet you once this image is further calibrated, this will have a longer tail."

Along with taking the spectra, the scientists measured the comet's brightness, comparing 3I/ATLAS's reflected sunlight to their reference points. This resulted in an estimated color and luminosity, suggesting that 3I/ATLAS is faint but steadily active, releasing gas and dust even at its current considerable distance from the sun.

Before the experts could dive any further in, the hosts of the event decided that two hours was enough time for one night. With the spectra captured and brightness measured and plenty of questions unanswered, the session wrapped on a note of anticipation, with many of us wishing we could return to the control room at Gemini South Observatory.

Thankfully, the Shadow the Scientists Initiative is planning another public viewing event after 3I/ATLAS re-emerges from the sun, this time using the Gemini North Observatory, which I for one am excited to join.

A stunning new telescope image has revealed the growing tail of the interstellar comet 3I/ATLAS. The luminous limb is starting to take shape as the icy interloper zooms ever closer to the sun on its one-way trip through the solar system.

3I/ATLAS is a roughly 7-mile-wide (11 kilometers) comet that was first spotted in early July and is zooming toward us from beyond the asteroid belt between Jupiter and Mars. Scientists quickly realized that the superfast object did not originate within our cosmic neighborhood. Instead, it was likely ejected from a distant star within the Milky Way and is now passing by us as it flies through the galaxy. It is unclear exactly where the comet originated, but initial findings hint that it is likely much older than the solar system.

On Aug. 27, astronomers at the Gemini South telescope in the Chilean Andes captured a detailed new photo of 3I/ATLAS, revealing the first clear look at the comet's tail. This plume of ice and dust is blown away from the comet by the solar wind, the stream of charged particles emanating from the sun. The tail is only starting to appear now, as the comet's frozen shell, or nucleus, soaks up more solar radiation, causing it to expel more particles from its icy surface. The tail will continue to grow as the comet gets closer to the sun in the coming months and will eventually become several times wider than the comet itself.

The new photo also shows a fuzzy cloud of ice and dust surrounding the comet. This cloud, known as a coma, will continue to swell as the comet is further heated by the sun. This will allow the comet to reflect more light that causes it to appear brighter in the night sky, although it will not become visible to the naked eye.

These classic cometary features are further proof that 3I/ATLAS is a natural object and not an extraterrestrial probe, which has been controversially proposed by some scientists with little to no supporting evidence.

Related: 8 strange objects that could be hiding in the outer solar system

3I/ATLAS is the third — and likely the largest — interstellar object ever discovered. It follows the past sightings of the mysterious object 'Oumuamua in 2017, which was also misidentified as a potential alien spacecraft, and Comet Borisov in 2019, which also grew a stunning tail.

The current extrasolar entity is shooting toward the sun at more than 130,000 mph (210,000 km/h) and will make a close approach to Mars next month, allowing Mars-orbiting spacecraft to get a better look at the comet and its tail, Live Science's sister site Space.com recently reported.

3I/ATLAS will reach perihelion, its closest point to the sun, on Oct. 29. But it will be on the opposite side of our home star as Earth, meaning we will lose sight of it during this time and may miss out on seeing its tail at its peak size. The comet will reach its minimum distance to Earth in December, when it will come within 170 million miles (275 million km) of our planet — around 700 times farther than Earth is from the moon — before beginning its long journey back out of the solar system.

Astronomers are racing to study the object as much as possible over the next year or so, to learn more about where it came from and how different star systems form and evolve. Recent observations from the James Webb Space Telescope hint that 3I/ATLAS has unusually high levels of water and carbon dioxide compared with other known comets. Additional photos of the comet, including a detailed shot from the Hubble Space Telescope and a colorful image from the Gemini North telescope in Hawaii, have also shed light on its composition.

Each new shot of the comet also acts as a permanent reminder of this rare cosmic encounter.

"As 3I/ATLAS speeds back into the depths of interstellar space, this [new] image is both a scientific milestone and a source of wonder," Karen Meech, an astronomer at the University of Hawaii and part of the Gemini observatories team, said in a statement. "It reminds us that our solar system is just one part of a vast and dynamic galaxy — and that even the most fleeting visitors can leave a lasting impact."

One of the advantages of having so many telescopes watching large parts of the sky is that, if astronomers find something interesting, there are probably images of it from before it was officially discovered sitting in the data archives of other satellites that no one thought to look at. That has certainly been the case for our newest interstellar visitor, 3I/ATLAS, which, though discovered in early July, had been visible on other telescopes as early as May.

We previously reported on Vera Rubin's detection of 3I/ATLAS well before it was officially found, and now a new paper has found the interstellar object in TESS's data going back to early May — and it looks like it may have been "active" around that time.

The Transiting Exoplanet Survey Satellite (TESS) isn't designed to find interstellar visitors, or anything faint for that matter. As its name implies, it is designed to look at stars (which are bright) and watch exoplanets traverse in front of them, watching the host star's light curve dip as they do. But, data is data, and since TESS happened to be looking at a part of the sky where 3I/ATLAS was supposed to be earlier this year, researchers Adina Feinstein and Darryl Seligman from Michigan State and John Noonan from Auburn decided to see if they could find any data on it in the telescopes archives.

Turns out they could, going as far back as May 7th, 2025, over the course of two separate observational periods. Since TESS captures an image every 200 seconds, and 3I/ATLAS is moving much more quickly than the traditional stars TESS is designed to look at, the team had to use a technique known as "shift-stacking". They predicted where the interstellar object (ISO) would be in each picture, shifted the pictures so the ISO would be at the same spot in every picture, and then stacked multiple of the pictures together to get a clear signal of an object that would otherwise be too faint to find in a single picture.

3I/ATLAS started the observational period at about 6.35 AU, and moved to about 5.47 AU by the end of a second window on June 2nd. During that time, its flux increased by a factor of 5, though the decrease in distance would have only accounted for an increased brightness about 1.5

Related: James Webb telescope images reveal there's something strange with interstellar comet 3I/ATLAS

There has already been plenty of speculation about what might be causing some of the more interesting features of 3I/ATLAS, ranging from mistakes in data collection to the object itself being alien technology. However, the authors have a much more mundane explanation for this seemingly bizarre occurrence — the ISO was likely outgassing "hypervolatile" materials like carbon dioxide and carbon monoxide. These have a much higher sublimation point than water ice, and can cause a significant increase in brightness, but most of the comets in our own solar system don't have any hypervolatiles left, so they wouldn't show the same dramatic increase in brightness that far away from the Sun. To the researchers, this is another data point that comets from other solar systems likely have a very different composition than those bound to ours.

In an effort to find even more differences, they also tried to look at the rotational period of the ISO's nucleus. However, there wasn't enough of a clear signal to delineate whether or not the nucleus was actually moving. Most likely this was caused by a coma obscuring any noticeable features, making it hard for TESS to detect any changes in brightness caused by its rotation.

As we continue to study every new interstellar object that comes across our path, we'll begin to find out more and more about them. This paper adds to that corpus of knowledge, and there will undoubtedly be more to come as astronomers start sifting through old data on every telescope they can find trying to unlock the mysteries of our enigmatic visitors.

The original version of this article was published on Universe Today.

Astronomers have found something strange in the James Webb Space Telescope's first images of interstellar comet 3I/ATLAS as it hurtles toward our sun, according to a new study.

The telescope's initial observations suggested that 3I/ATLAS has one of the highest carbon dioxide (CO2) to water (H2O) ratios ever recorded in a comet. This unusual chemistry, if confirmed, could shed light on 3I/ATLAS' mysterious origins beyond our solar system.

Scientists have been using various telescopes to learn all they can about 3I/ATLAS since its discovery in July. The extremely rare comet is only the third confirmed interstellar object ever recorded, and researchers are keen to study its makeup before the intruder whizzes past our sun in October and exits the solar system for good.

The first James Webb Space Telescope (JWST) observations took place on Aug. 6, with researchers making use of the JWST's near-infrared spectrograph to decipher the comet's physical properties based on the light it emits. They reported their findings Monday (Aug. 25) in a preprint paper posted on the European research repository Zenodo, so they have not yet been peer-reviewed.

Comets develop an atmosphere, or coma, as they fly by stars. This cloud of gas and dust grows larger and brighter the closer a comet gets to a star, with ice and other materials on the comet heating up and releasing gas in a process called outgassing. The JWST imaging revealed that 3I/ATLAS' coma was dominated by carbon dioxide, according to the study.

The researchers noted that the high carbon dioxide content could be linked to exposure to radiation or where the comet formed in relation to the distance at which CO2 froze (the CO2 ice line) around its parent protoplanetary disk — the swirling gas and dust that surrounds young stars and from which planets, comets and asteroids are born.

"Our observations are compatible with an intrinsically CO2-rich nucleus, which may indicate that 3I/ATLAS contains ices exposed to higher levels of radiation than Solar System comets, or that it formed close to the CO2 ice line in its parent protoplanetary disk," the researchers wrote in the study.

Related: Interstellar comet 3I/ATLAS transforms into a giant 'cosmic rainbow' in trippy new telescope image

Astronomers are learning more about 3I/ATLAS with each new observation. Their findings so far indicate that the comet is whizzing along at speeds in excess of 130,000 mph (210,000 km/h) in an unusually flat and straight trajectory that is unlike anything else in the solar system.

Initial size estimates put the comet at around 7 miles (11 kilometers) wide. However, subsequent data from the Hubble Space Telescope suggested that 3I/ATLAS is probably closer to a maximum of 3.5 miles (5.6 km) across. Either way, it's likely the largest interstellar object ever seen. 3I/ATLAS could also be the oldest comet ever seen, with one study suggesting it's around 3 billion years older than our 4.6 billion-year-old solar system. It's currently unclear where the comet came from.

That hasn't stopped some from speculating. Last month, a controversial preprint study explored the idea that 3I/ATLAS could be a piece of "possibly hostile" extraterrestrial technology in disguise. However, experts told Live Science that the study's claims were "nonsense" and "insulting."

The speed of the comet, which has the highest velocity ever recorded for a solar system visitor, is evidence that 3I/ATLAS has been on the move for billions of years, gaining momentum from a gravitational slingshot effect as it whips by stars and nebulas, according to a NASA statement released earlier this month following the Hubble Space Telescope observations.

"No one knows where the comet came from," David Jewitt, an astronomer at UCLA and science team leader for the Hubble observations, said in the statement. "It's like glimpsing a rifle bullet for a thousandth of a second. You can't project that back with any accuracy to figure out where it started on its path."

NASA has revealed the most detailed images yet taken of comet 3I/ATLAS, the interstellar visitor that is currently barreling its way through our solar system.

The images, taken by NASA's Hubble Space Telescope, have enabled astronomers to more accurately estimate the space object's size — and it looks like it's smaller than we thought, NASA said in a statement.

3I/ATLAS was first discovered on July 1, and the next day it was confirmed by NASA to have originated from outside of our solar system. The extrasolar entity is hurtling toward the inner solar system at speeds of more than 130,000 mph (210,000 km/h) and is expected to reach its closest point to the sun in late October. (The object poses no threat to us, and will be on the far side of the sun during its close approach).

It is only the third such interstellar object to have been detected in our solar system, and astronomers are still scratching their heads as to where it came from and what it is made of.

"No one knows where the comet came from," David Jewitt, an astronomer at UCLA and science team leader for the Hubble observations, said in the statement. "It's like glimpsing a rifle bullet for a thousandth of a second. You can't project that back with any accuracy to figure out where it started on its path."

Related: 3I/ATLAS: Everything you need to know about the new 'interstellar visitor' shooting through the solar system

At the end of July, the newly operational Vera C. Rubin Observatory estimated that the alien comet was roughly 7 miles (11.2 kilometers) wide across its icy nucleus. Now, Hubble's images have suggested that the nucleus is probably closer to a maximum of 3.5 miles (5.6 km) across, which would still make it the largest interstellar object ever spotted. On the low end, NASA estimates the comet to be no smaller than 1,000 feet (320 meters) across — but planned observations with the James Webb Space Telescope and other NASA observatories will further hone these numbers as the comet gets closer over the coming months.

The two other known interstellar objects that have blown through our solar system are 1I/'Oumuamua, which was discovered in 2017, and 2I/Borisov, which was spotted in 2019. 'Oumuamua, an asteroid, is believed to have been around 0.2 miles (0.4 km) wide), while Comet Borisov has a nucleus measuring roughly 0.6 miles (1 km) wide — making both significantly smaller than the upper estimates for 3I/ATLAS.

Researchers hope that by studying these alien objects we can learn more about distant star systems and the characteristics of the exoplanets that orbit within them.

"Each one of these ISOs [interstellar objects] is a little piece of low-hanging fruit from a tree that can tell us a great deal about the trees growing in some other neighborhood," Wes Fraser, an astronomer with National Research Council Canada, previously told Live Science.

The alien comet 3I/ATLAS is roughly 7 miles (11.2 kilometers) wide, making it the largest interstellar object ever spotted, according to newly revealed photos from the Vera C. Rubin Observatory.

The detailed images, which were captured before the extrasolar entity was officially discovered, highlight the immense power of the record-breaking telescope and demonstrate how valuable it will be for finding future interstellar interlopers, researchers say.

3I/ATLAS was discovered on July 1, barrelling toward the sun at more than 130,000 mph (210,000 km/h). Less than 24 hours later, NASA had confirmed that it was the third known interstellar object (ISO) — an ejected piece of an alien star system that is shooting clean through our solar system. It quickly became clear that 3I/ATLAS was a comet, and computer simulations tracing back its likely region of origin hint that it could be up to 3 billion years older than Earth, potentially making it the oldest comet ever detected.

Until now, all researchers have been able to uncover about the comet's size was that its coma — the cloud of ice, dust and gas surrounding it — was up to 15 miles (24 km) across. However, the size of its icy nucleus, or outer shell, remained a mystery.

But in a new study, uploaded July 17 to the preprint server arXiv, a group of more than 200 researchers was able to find images of the comet in Vera C. Rubin's extensive early data set, revealing the nucleus's likely size.

The images, which were snapped on June 21, suggest that the comet's nucleus has a likely radius of around 3.5 miles — or a diameter of about 7 miles — with a margin of error equal to around 0.4 mile (0.7 km).

Related: Interstellar comet 3I/ATLAS transforms into a giant 'cosmic rainbow' in trippy new telescope image

Until now, only two other ISOs have ever been confirmed: 1I/'Oumuamua, an asteroid that was discovered in 2017; and 2I/Borisov, a comet spotted in 2019. Astronomers have, however, long suspected that many more ISOs have passed through the solar system undetected.

'Oumuamua is believed to be around 0.2 mile (0.4 km) wide, although its exact shape was unclear, while Comet Borisov has a nucleus roughly 0.6 mile (1 km) wide. This means that 3I/ATLAS is comfortably the largest ISO ever seen.

The new study has also given scientists a good look at the comet's coma and helped to identify large amounts of dust and water ice surrounding its nucleus. These additional findings are further evidence that 3I/ATLAS is a natural comet — not a disguised probe sent here by an advanced alien civilization, as some researchers have controversially proposed in recent weeks.

The Vera C. Rubin Observatory, located in the Chilean Andes, is equipped with the world's largest digital camera, which is about to begin a 10-year mission to scan the Southern Hemisphere's skies, known as the Legacy Survey of Space and Time (LSST). The telescope released its first images in June, revealing more than 10 million galaxies in unprecedented detail, and has already discovered thousands of new asteroids.

The fact that the newly released photos could determine 3I/ATLAS' size, 10 days before the object was discovered, is proof of what Vera C. Rubin will be able to accomplish when it is fully switched on later this year, the study team wrote.

Many experts believe that the observatory will revolutionize the study of ISOs and predict that it could spot up to 50 new alien interlopers within the next decade, according to Forbes.

The newly discovered interstellar object 3I/ATLAS could be a piece of "possibly hostile" extraterrestrial technology in disguise, according to controversial research from a small group of scientists, including a renowned alien-hunting astronomer.

Their paper, which has not been peer-reviewed, echoes similar claims previously made about 'Oumuamua, the first-ever cosmic interloper that was discovered in 2017.

But experts have told Live Science that the new claims are "nonsense" and "insulting," and insist that the available evidence points toward the object being completely natural.

3I/ATLAS was discovered on July 1 barreling toward the sun at more than 130,000 mph (210,000 km/h), and was confirmed to be an interstellar object less than 24 hours later. Initial observations strongly suggest it is a large comet surrounded by a cloud of ice, gas and dust called a coma, stretching up to 15 miles (24 kilometers) across. A computer model simulating where it originated from hinted that it could be up to 3 billion years older than our solar system, potentially making it the oldest comet ever seen.

But in a new paper, uploaded July 16 to the preprint server arXiv, a trio of researchers have questioned whether the comet is actually some form of covert alien tech sent here by an advanced, potentially aggressive extraterrestrial civilization.

The researchers described the new paper as a "pedagogical exercise," or thought experiment, and offer no clear evidence of alien involvement. Instead, they point at the comet's "anomalous characteristics" and provide alternative theories to explain them.

Related: Interstellar comet 3I/ATLAS transforms into a giant 'cosmic rainbow' in trippy new telescope image

The study's most notable author is Avi Loeb, an astronomer at Harvard University who is renowned for linking extraterrestrial objects to intelligent aliens. He is the head of the Galileo Project, which is attempting to detect evidence of technosignatures and UFOs. In 2023, he led a controversial expedition that claimed to have collected pieces of possible alien tech left behind by an unconfirmed interstellar meteorite in the Pacific Ocean. (These claims have since been largely debunked by outside researchers).

Loeb was also the primary researcher who claimed that the unusual shape and non-gravitational acceleration of the interstellar object 'Oumuamua were signs that it was an alien probe.

Today, the general consensus is that 'Oumuamua was an asteroid that was leaking gas into space, similar to a comet. However, Loeb and his colleagues have continued to advocate its potential alien origin and have proposed missions to track down the wandering space rock.

Loeb's co-authors for the new study are both associated with the Initiative for Interstellar Studies (i4is), a U.K. institute dedicated to planning future missions to alien star systems.

In a blog post explaining the new paper, Loeb wrote that if 3I/ATLAS is a "technological artifact" it could be evidence of the dark forest hypothesis, which argues that the reason we have not found evidence of extraterrestrial life is that they are staying silent to remain invisible to potential predators or prey.

"The consequences, should the hypothesis turn out to be correct, could potentially be dire for humanity, and would possibly require defensive measures to be undertaken," he wrote.

Alien 'evidence'

Most of the points laid out in the new paper relate to the unusual trajectory of 3I/ATLAS. The object is moving significantly faster than the only other known interstellar objects — 'Oumuamua and Comet Borisov, which was spotted in 2019 — and has entered the solar system at a different angle from its predecessors, approaching the sun side-on relative to our star's orbit through the Milky Way.

Loeb wrote that the object's trajectory "offers various benefits to an extraterrestrial intelligence" that may be using it to subtly spy on Earth. One such benefit is that 3I/ATLAS will make relatively close approaches to three planets: Jupiter, Mars and Venus. And the minimum distances between the object and these worlds could enable aliens to discretely deploy "gadgets" there, Loeb wrote.

3I/ATLAS will also be hidden on the opposite side of the sun to Earth when it reaches its closest point to our home star in late October. "This could be intentional to avoid detailed observations from Earth-based telescopes when the object is brightest or when gadgets are sent to Earth from that hidden vantage point," Loeb wrote.

The unusually high speed of 3I/ATLAS also makes it very hard to launch a spacecraft to intercept it before it exits the solar system, which could be another potential sign of clandestine alien activity, the researchers argued.

Based on its current speed, Loeb also noted that 3I/ATLAS would have entered the outer boundaries of the solar system around 8,000 years ago, which is "roughly when human-made technologies became advanced enough to start documenting history on Earth." Although, it is unclear what he is trying to imply by saying this.

The researchers also argued that there is insufficient evidence to show conclusively that 3I/ATLAS is a comet, especially as researchers are yet to identify any "volatiles," or specific chemicals associated with comets, within its coma.

Controversial claims

Since 3I/ATLAS was discovered, researchers have been trying to identify it, and so far, the overwhelming consensus is that it is a comet.

"There have been numerous telescopic observations of 3I/ATLAS demonstrating that it's displaying classical signatures of cometary activity," Darryl Seligman, an astronomer at Michigan State University who led the first study quantifying 3I/ATLAS, told Live Science in an email.

"All evidence points to this being an ordinary comet that was ejected from another solar system, just as countless billions of comets have been ejected from our own solar system," added Samantha Lawler, an astronomer at the University of Regina in Canada who specializes in solar system dynamics.

Any assumptions about the object's lack of volatiles is also premature at this time. "The object is still pretty far away from the sun, so no, we wouldn't typically expect to find direct evidence of volatiles necessarily," Seligman said. Instead, these compounds will likely become apparent in the coming weeks and months, he added.

Loeb admits that the alien technology scenario is a long shot: "By far, the most likely outcome will be that 3I/ATLAS is a completely natural interstellar object, probably a comet," he wrote in the blog post.

Given the available evidence, many of the researchers who spoke to Live Science are disappointed with the new paper and pointed out that it distracts from the work of other scientists.

"Astronomers all around the world have been thrilled at the arrival of 3I/ATLAS, collaborating to use advanced telescopes to learn about this visitor," Chris Lintott, an astronomer at the University of Oxford who was part of the team that simulated 3I/ATLAS's galactic origins, told Live Science in an email. "Any suggestion that it's artificial is nonsense on stilts, and is an insult to the exciting work going on to understand this object."

Loeb is no stranger to this type of criticism and has defended his position, writing that "the hypothesis is an interesting exercise in its own right, and is fun to explore, irrespective of its likely validity."

However, while it is important to remain open-minded about any "testable prediction," the new paper pushes this sentiment to the limit, Lawler told Live Science in an email. "In my experience, the vast majority of scientists subscribe to the idea that extraordinary claims require extraordinary evidence, and the evidence presented is absolutely not extraordinary."

The newly discovered "interstellar visitor" 3I/ATLAS can be seen shining like a rainbow-colored string of cosmic pearls in a trippy new timelapse image captured by a telescope in Hawaii.

The interloper was discovered on July 1, and within 24 hours NASA confirmed it was an interstellar object — an ejected piece of an alien star system that is shooting through our cosmic neighborhood. It is only the third object of its kind ever spotted, and is most likely a large comet, stretching up to 15 miles (24 kilometers) across.

Initial observations also suggest that it could be up to 3 billion years older than the solar system, potentially making it the oldest comet ever seen.

The extrasolar entity is hurtling toward the sun at more than 130,000 mph (210,000 km/h). It will reach its closest point to our home star, or perihelion, in late October, before beginning its long journey back out of the solar system. Therefore, scientists only have a limited time to study the object before it is gone forever.

Astronomers at the Gemini North telescope, located on the summit of Hawaii's Mauna Kea volcano, have been closely watching 3I/ATLAS since its discovery. And on Tuesday (July 15), they released several stunning images, including a close-up shot of the comet's coma — the cloud of ice, gas and dust that surrounds a comet's icy shell — and a technicolor timelapse photo of the interloper moving through space.

Related: Watch newly discovered 'interstellar visitor' 3I/ATLAS shoot toward us in first livestream

The timelapse photo is a combination of at least 16 different photos taken using three different filters, making the comet appear to shift between blue, red and green hues as it moves across the sky. In reality, the comet gives off a white light, as seen in the coma photo.

The photos have helped provide astronomers with "critical early characterization of this interstellar wanderer," Martin Still, the National Science Foundation program director for the International Gemini Observatory, which includes Gemini North and its sister telescope, Gemini South, in the Chilean Andes, said in a statement. "We look forward to a bounty of new data and insights as this object warms itself on sunlight before continuing its cold, dark journey between the stars."

3I/ATLAS

Until now, only two other interstellar objects have ever been confirmed: 1I/'Oumuamua, an unusual asteroid discovered in 2017; and 2I/Borisov, a pristine comet spotted in 2019. However, researchers suspect that many more alien interlopers have passed through the solar system unnoticed.

3I/ATLAS is significantly larger than its predecessors and is traveling at a much faster rate. It also originates from a completely different part of the Milky Way than 'Oumuamua or Comet Borisov, making it an intriguing target for future study.

Astronomers hope to be able to learn more about the comet's exact origins as the sun starts to melt away its outer icy layers over the coming months, potentially unleashing a gigantic cometary tail that can be studied in great detail by space assets, such as the James Webb Space Telescope.

3I/ATLAS will make its closest approach to Earth in mid-December, after temporarily disappearing behind the sun in October and November. Its minimum distance from our planet will be around 1.6 times the distance between Earth and the sun, meaning that it "poses no threat" to us, according to NASA.

It will remain too distant to be seen by the naked eye, but it is expected to brighten to the point where it can be seen with a decent backyard telescope or pair of stargazing binoculars. The best time to see it for yourself will likely be in early 2026.

The mysterious "interstellar visitor" that was recently spotted whizzing through the solar system may be around 3 billion years older than our cosmic neighborhood, a new study suggests. If confirmed, the alien interloper would be the oldest comet ever seen from Earth. And, if it's made of what researchers think it is, it may also grow a spectacularly long tail in the coming months.

3I/ATLAS is an interstellar comet, potentially up to 15 miles (24 kilometers) across, that is currently shooting toward the sun at more than 130,000 mph (210,000 km/h). Once it passes its closest point to our home star, or perihelion, in late October, the extrasolar entity will begin its long journey back out of the solar system, before eventually leaving us behind forever.

The cosmic visitor was discovered July 1 and was confirmed as an interstellar object by NASA less than 24 hours later. Ever since, the astronomical community has been racing to uncover as much as they can about the alien comet.

In a new study, uploaded July 7 to the preprint server arXiv and presented July 11 at the Royal Astronomical Society's National Astronomy Meeting in Durham, England, researchers used a computer model to simulate where 3I/ATLAS may have originated from. The team found that the comet likely originates from the Milky Way's "thick disk" — a population of stars located above and below the main disk where the sun and a majority of our galaxy's stars reside.

Most of the stars in this part of the galaxy are believed to be billions of years older than our solar system, and because comets are made up from the leftovers of the protoplanetary disks that surround new stars, it is highly likely that 3I/ATLAS could be just as old.

Related: Watch newly discovered 'interstellar visitor' 3I/ATLAS shoot toward us in first livestream

"Our statistical method suggests that 3I/ATLAS is very likely to be the oldest comet we have ever seen," study lead author Matthew Hopkins, a doctoral candidate at the University of Oxford in the U.K., said in a statement. However, the new findings have not yet been peer-reviewed, and more observations are needed to determine exactly how old the comet is.

The study team used a novel computer program, known as the Ōtautahi-Oxford model, which helps predict where interstellar objects (ISOs) come from using data from the European Space Agency's Gaia space observatory.

Hopkins designed the model while working toward completing his PhD, and he had only finished defending his doctoral thesis on the topic around a week before 3I/ATLAS was discovered, providing an immediate chance to put his theories to the test.

"It's a fantastic opportunity to test our model on something brand new and possibly ancient," Hopkins said.

Interstellar origins

Only two other ISOs have been discovered to date: 1I/'Oumuamua, an asteroid that was discovered in 2017; and 2I/Borisov, a comet spotted in 2019.

Both 'Oumuamua and Comet Borisov entered the solar system head-on to the sun, relative to our home star's trajectory through the Milky Way, hinting they come from the galaxy's main disk. But 3I/ATLAS is coming at us side-on, meaning it has a totally different origin from the previous ISOs.

"This is an object from a part of the galaxy we've never seen up close before," study co-author Chris Lintott, an astronomer at the University of Oxford, said in the statement. "We think there's a two-thirds chance this comet is older than the solar system, and that it's been drifting through interstellar space ever since," he added.

As we collect more data about 3I/ATLAS, the researchers will continue to refine their model to further pinpoint where the alien interloper may have originated from. However, even then, there are limits to how precisely scientists can track its interstellar origins.

"We probably won't ever be able to pin it down to a single star system," Aster Taylor, a graduate student at the University of Michigan who was not involved in the new study, previously told Live Science.

A spectacular tail?

Understanding where 3I/ATLAS came from can also help researchers predict how it will behave when it shoots past the sun later this year.

Experts predict that planetary systems within the thick disk might have an abundance of water, meaning that 3I/ATLAS could be rich with water ice. If this is the case, it means the comet could likely grow a large cometary tail in the coming months, as the sun vaporizes its outer layers, the researchers wrote.

The cloud of ice, dust and gas that surrounds the comet, known as its coma, could also become much larger, allowing it to reflect more sunlight and appear much brighter to us, making it even more visually stunning as it approaches Earth.

However, the interstellar comet won't be visible to the naked eye, meaning you will require a decent backyard telescope or a pair of stargazing binoculars to see it for yourself. The best time to see it will likely be in late 2025 and early 2026, the researchers wrote.

The astronomical community is abuzz over a newly discovered "interstellar object," only the third of its kind ever seen, which is currently shooting toward us on a one-way trip through the solar system.

The race is now on to study the alien interloper, named 3I/ATLAS, before it leaves forever.

"We only have one shot at this object and then it's gone forever," Darryl Seligman, an astronomer at Michigan State University and the lead author of a new paper about the object, told Live Science. "So we want as much information from all of our observatories as we can possibly get."

Related: Watch newly discovered 'interstellar visitor' 3I/ATLAS shoot toward us in first livestream

Experts say studying 3I/ATLAS could potentially tell us about alien star systems and how exoplanets form — and we may even be able to trace it back to its origins.

Initial discovery

3I/ATLAS was discovered on July 1 from data collected by the Asteroid Terrestrial-impact Last Alert System (ATLAS) and immediately piqued researchers' interests due to its trajectory and extreme speed, which exceeds 130,000 mph (210,000 km/h). Within 24 hours of its discovery, NASA had confirmed that it was an interstellar object.

A day later (July 3), a group of more than 40 astronomers, led by Seligman, had uploaded the first paper describing the extrasolar entity to the preprint database arXiv. All data so far indicates that 3I/ATLAS is a large comet surrounded by a cloud of ice, dust and gas up to 15 miles (24 kilometers) across.

Prior to this discovery, only two other interstellar objects (ISOs) had been spotted: 1I/'Oumuamua, a space rock that was discovered in 2017; and 2I/Borisov, a comet spotted in 2019. This makes the newly discovered comet particularly appealing to astronomers.

However, there is a limited window to study 3I/ATLAS. The comet, which is currently around 4.5 times farther from the sun than Earth, will reach its closest point to the sun, or perihelion, on Oct. 30, before beginning its journey out of the solar system, when it will get much harder to spot. It will also be out of view between late September and early December, when it is positioned on the opposite side of the sun to Earth.

Observing an interstellar visitor

Over the next few weeks and months, researchers will attempt to use "any and all telescopes" they can to make observations of 3I/ATLAS, Sean Raymond, a planetary scientist at the University of Bordeaux in France, told Live Science in an email.

This will be especially true for observatories in the Southern Hemisphere, which will have a better view of the increasingly bright comet, Aster Taylor, a graduate student at the University of Michigan and co-author of the arXiv study, told Live Science in an email.

Experts are particularly excited about the possibility of imaging 3I/ATLAS with the Vera C. Rubin Observatory — the world's most powerful optical telescope, which recently released its first images. The observatory, located in Chile, has already proved to be adept at imaging never-before-seen asteroids and will undoubtedly target the interstellar comet when it comes fully online in a few months time.

The James Webb Space Telescope (JWST) and Hubble Space Telescope, meanwhile, could help reveal the interloper's chemical composition because of their ability to study the object in multiple wavelengths of the electromagnetic spectrum Pedro Bernardinelli, a planetary scientist at the University of Washington's DiRAC Institute, told Live Science in an email.

Some researchers have also proposed using NASA's Mars rovers to snap pictures of the comet as it makes a close pass by the Red Planet a few weeks before it reaches perihelion. The robots have previously been used to spy on dangerous sunspots lurking on the sun's far side from Earth.

Another intriguing option is to send a spacecraft to collect samples from 3I/ATLAS. However, the general consensus among experts is that such a mission is unlikely to happen

Alien star systems

Studying 3I/ATLAS provides a rare opportunity for us to glean insights into alien star systems and potential exoplanets.

"Interstellar objects are probably the leftovers of the formation of exoplanets," Raymond said. "Studying them can open a window into understanding other planetary systems' formation and evolution."

In this way, ISOs like 3I/ATLAS also "connects the solar system with its galactic environment," Amir Siraj, a doctoral candidate at Princeton University who has previously studied ISOs, told Live Science.

While it is still unclear where 3I/ATLAS came from, it's possible we can pinpoint its origins, especially if researchers can work out how old it is, Wes Fraser, an astronomer with National Research Council Canada, told Live Science in an email. And as the comet reaches perihelion, the amount of ice and other "volatile" substances that get burned off the interloper will help us narrow this down, Fraser added.

However, even then "we probably won't ever be able to pin it down to a single star system," Taylor argued.

The solar system has an uninvited guest that is currently shooting toward us on a one-way trip through our cosmic neighborhood.

The newly discovered interstellar visitor, named 3I/ATLAS, is only the third of its kind ever seen.

It was discovered on July 1 and immediately raised eyebrows because of its high speed and extreme trajectory, which suggested it would pass straight through the solar system. Within 24 hours, NASA confirmed that the object does not belong here and is destined to leave again.

The extrasolar entity, which is likely a comet, is barreling toward us at more than 130,000 mph (210,000 km/h) and will reach its closest point to the sun in late October, before beginning its long journey back out toward interstellar space.

Related: Watch newly discovered 'interstellar visitor' 3I/ATLAS shoot toward us in first livestream

But the discovery raises lots of questions about 3I/ATLAS, such as where it came from, what it's made of, when it will be closest to Earth and how researchers can best study it.

What are interstellar objects?

An interstellar object (ISO) is anything that originates from outside the sun's sphere of influence. This includes asteroids and comets that have been gravitationally captured by, and now permanently reside within, our solar system. However, we currently have no system for spotting these objects.

Therefore, the only confirmed ISOs we know about are the ones that we have seen zooming through the solar system at high speeds.

Only two other ISOs have ever been confirmed: 1I/'Oumuamua, a space rock that was discovered in 2017; and 2I/Borisov, a comet spotted in 2019. However, astronomers have long assumed that there are many more ISOs that we cannot see.

A potential ISO exploded in the skies above Papua New Guinea in 2014. However, this remains inconclusive.

How was 3I/ATLAS discovered?

3I/ATLAS was first spotted in data collected between June 25 and June 29 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), which automatically scans the night sky using telescopes in Hawaii, Chile and South Africa. The object was initially dubbed A11pl3Z before receiving its official designation.

Multiple other researchers then quickly established that the object was an ISO using data going back to June 15, according to NASA.

More than 40 researchers collated their results into a paper uploaded July 3 to the preprint server arXiv, which was the first study written about the new object.

The discovery of 3I/ATLAS was a group effort, and a reminder of the importance of cooperation, study lead author Darryl Seligman, an astronomer at Michigan State University, told Live Science in an email. "We only have one shot at this object and then it's gone forever," he added. "So we want as much information from all of our observatories as we can possibly get."

What do we know about 3I/ATLAS?

Researchers initially assumed that 3I/ATLAS was an asteroid. However, in subsequent observations, the object looks more similar to a comet.

The interloper has displayed "tentative signs of cometary activity" — including being surrounded by a bright cloud of gas and ice, known as a coma, and having what looks like a tail — according to the International Astronomical Union's Minor Planet Center. Its proposed comet name is C/2025 N1 (ATLAS).

3I/ATLAS is different from its predecessors due to its size, although "it's hard to measure its size right now," Aster Taylor, a graduate student at the University of Michigan and co-author of the new study, told Live Science in an email.

The researchers estimate that the comet and its coma are up to 15 miles (24 kilometers) across, making it significantly bigger than 'Oumuamua or Comet Borisov, which were both less than a mile (1.6 km) wide. It is also traveling faster, on a straighter trajectory, than those other two interstellar objects.

The past two objects have come toward the sun head-on compared to our home star's trajectory through the Milky Way, but 3I/ATLAS is coming side-on, or perpendicular to the sun's trajectory, Wes Fraser, an astronomer with National Research Council Canada, told Live Science in an email. "It's peculiar to say the least."

Does 3I/ATLAS pose a hazard to Earth?

3I/ATLAS was around 4.5 astronomical units (AU) from the sun when it was discovered, or 4.5 times the distance between Earth and the sun.

It will reach its closest point to the sun, or perihelion, on Oct. 30, coming within 1.5 AU of our home star. Shortly before this happens, the object will also make its closest approach to Mars, coming within 0.4 AU of the Red Planet. But the comet will make its closest approach to our planet in December, on its journey back out of the solar system. As a result, "the comet poses no threat to Earth and will remain at a [minimum] distance of at least 1.6 astronomical units," NASA officials wrote.

While the object is currently too faint for backyard stargazers to see, it will brighten significantly as it moves toward the sun and should be visible in the coming months, according to Spaceweather.com.

Where did 3I/ATLAS come from?

Researchers are keen to work where 3I/ATLAS comes from. Another study uploaded to the preprint server arXiv on July 7 suggests that it likely came from the Milky Way's "thick disk," which accounts for around two-thirds of our galaxy's stars. However, researchers will need much more information to pin down a more accurate loacation.

"But it really could have come from any number of stars, not necessarily local ones," Fraser noted.

While we know what general direction the object is coming from, it is hard to match it to a potential star system without knowing how old it is. The comet could have been "wandering for a few billion years before paying us a chance visit," Amir Siraj, a doctoral candidate at Princeton University who has previously studied interstellar objects, told Live Science in an email.

Although we have only just discovered 3I/ATLAS, it has likely been with us for quite some time.

It likely came within the orbit of Neptune in mid-2023 and will head back past the distant gas giant in early 2028, Marco Micheli, an astronomer at the European Space Agency's Near Earth Object Coordination Centre who helped discover 'Oumuamua, told Live Science in an email. Depending on where you define the edge of the solar system to be, it could take up to several decades for an ISO to pass completely through, he added.

Is 3I/ATLAS an alien probe?

It is extremely unlikely that 3I/ATLAS has any ties to an extraterrestrial civilization.

When 'Oumuamua was discovered in 2017, some experts claimed that the ISO could have been a disguised spacecraft due to anomalies in its acceleration.

However, because 3I/ATLAS seems to behave like a regular comet, the same theory has not been proposed so far.

Nevertheless, some researchers are still keen to study the ISO for similar reasons: Avi Loeb, an astronomer at Harvard University who first proposed the theory that 'Oumuamua was extraterrestrial tech, has proposed using JWST to search for signs of "non-gravitational acceleration" from the comet, via a post he wrote on Medium.

Could we visit 3I/ATLAS?

We've sent probes to other objects like 3I/ATLAS before. For instance, in 2020, NASA's OSIRIS-REx mission successfully landed on the potentially hazardous asteroid Bennu, collected samples and later returned them to Earth.

Researchers had previously proposed similar missions for 'Oumuamua, as well as for future ISOs. But this is unlikely for 3I/ATLAS: "It may be possible theoretically, but we don't have any missions prepared that could do this, so we won't be able to," Taylor said.

The current "funding landscape" following the proposed cuts to NASA's budget also makes a mission unlikely, Seligman added.

When could we spot the next interstellar object?

Experts told Live Science that ISOs pass through the solar system much more frequently than we spot them, although it's unknown how often this happens.

Moving forward, experts believe we will get better at spotting interstellar interlopers thanks to the Vera C. Rubin Observatory, which recently captured its first images and is already finding new asteroids.

"I'm expecting this to become a more frequent event," Micheli said.

We could see the next ISO in "as quick as a year," Taylor added, while Fraser believes we could start finding one "every two years" from now on.

With each discovery, researchers will be able to learn more about alien star systems and the exoplanets that reside within them: "Each one of these ISOs is a little piece of low-hanging fruit from a tree that can tell us a great deal about the trees growing in some other neighbourhood," Fraser said.

A mysterious, uninvited guest has been spotted shooting through the solar system at breakneck speed. And, for the first time, you can now see this interstellar visitor barreling towards us for yourself — thanks to a free livestream from the Virtual Telescope Project.

The newly discovered interloper, initially dubbed A11pl3Z, was revealed to us on Tuesday (July 1), when researchers spotted it in data collected by the Asteroid Terrestrial-impact Last Alert System (ATLAS), which automatically scans the night sky using telescopes in Hawaii, Chile and South Africa.

The mysterious object is traveling toward the sun at around 152,000 mph (245,000 km/h), and it is set on a very flat and straight trajectory, unlike any other known object in our solar system.

Many experts initially predicted that it was an interstellar object, meaning it originates from beyond the sun's gravitational influence and has enough momentum to shoot straight through our cosmic neighborhood without slowing down. On Wednesday (July 2), NASA confirmed this and revealed that the interloper is most likely a comet. It has now been officially named 3I/ATLAS.

The extrasolar entity is too faint to be visible to the naked eye or through amateur stargazing equipment, although it may brighten sufficiently to become visible to backyard telescopes in the coming weeks and months. However, the upcoming livestream from the Virtual Telescope Project (VTP) will share the view from VTP's powerful telescope in Manciano, Italy.

The livestream was recorded on July 3 and can be viewed on the VTP's YouTube channel.

Related: 1 million 'interstellar objects' — each larger than the Statue of Liberty — may lurk in the outer solar system

Only two other confirmed interstellar visitors have ever been spotted before now: Comet 2I/Borisov, which was seen shooting through the solar system in 2019; and 'Oumuamua, a cigar-shaped object that made headlines in 2017 when some astronomers argued it was potentially an alien probe, before experts showed it was most likely a hydrogen-spewing space rock. However, scientists suspect that many more interstellar interlopers likely pass through our cosmic neighborhood undetected.

3I/ATLAS is believed to measure up to 12 miles (20 kilometers) across and is currently around 4.5 times as far from the sun as Earth is. It will reach its closest point to the sun, known as perihelion, on Oct. 30, coming within 1.4 Earth-sun distances, or astronomical units (AU), of our home star. Shortly before this happens, the comet will also make its closest approach to Mars, coming within 0.4 AU of the Red Planet.

Earth will be on the opposite side of the sun to 3I/ATLAS during the comet's solar flyby. The object will likely make its closest approach to Earth in December, on its journey back out of the solar system. As a result, "the comet poses no threat to Earth and will remain at a [minimum] distance of at least 1.6 astronomical units," NASA officials wrote in a statement.

Astronomers are now racing to learn more about the rare object before it leaves the solar system at some point next year. Researchers will be able to study it until the end of September, when it will become obscured by the sun's light, and again from December, when the comet reemerges from behind our home star.

The interstellar visitor will likely be imaged by the Vera C. Rubin Observatory — the world's most powerful optical telescope, which recently released its first images.

Some researchers have also suggested using the James Webb Space Telescope and NASA's Mars rovers to photograph the object as it shoots toward the sun.

NASA scientists have confirmed that a mysterious object shooting toward us through the solar system is an "interstellar object" — only the third of its kind ever seen. Experts have also given the cosmic interloper an official name, and revealed new information about its origins and trajectory.

News of the extrasolar entity, initially dubbed A11pl3Z, broke on Tuesday (July 1), when NASA and the International Astronomical Union (IAU) both listed it as a confirmed object. It was first discovered in data collected between June 25 and June 29 by the Asteroid Terrestrial-impact Last Alert System (ATLAS), which automatically scans the night sky using telescopes in Hawaii, Chile and South Africa. Multiple telescopes across the world have subsequently spotted the object in observation data that date back to June 14.

The object is traveling toward the sun extremely fast, at around 152,000 mph (245,000 km/h), and observations suggest that it is set on an extremely flat and straight trajectory, unlike anything else in the solar system. This led many experts to speculate that it originated from beyond the sun's gravitational influence and has enough momentum to shoot straight through our cosmic neighborhood without slowing down.

On Wednesday (July 2), NASA released a statement confirming that A11pl3Z is indeed an interstellar object and will not remain in the solar system for long. The researchers also shared the object's new official name, 3I/ATLAS, and revealed that it is most likely a comet, upending previous assumptions that it was an asteroid. The object's full comet name is C/2025 N1 (ATLAS).

Until now, only two confirmed interstellar visitors have ever been spotted: Comet 2I/Borisov, which was seen sailing through the solar system in 2019; and 'Oumuamua, a cigar-shaped object that made headlines in 2017 when some astronomers argued it was potentially an alien probe, before experts showed it was most likely a hydrogen-spewing space rock.

But scientists have long suspected that many more interstellar interlopers likely pass through our cosmic neighborhood without ever being detected.

Related: 1 million 'interstellar objects' — each larger than the Statue of Liberty — may lurk in the outer solar system

Researchers initially suspected that 3I/ATLAS was an asteroid, like 'Oumuamua. However, the object has displayed "tentative signs of cometary activity" like 2I/Borisov — including being surrounded by a bright cloud of gas and ice, known as a coma, and having what looks like a tail — according to the IAU's Minor Planet Center. However, more observations are needed to confirm this.

There has been no additional information about the potential comet's size or shape: The current best guess is that it could be up to 12 miles (20 kilometers) across. However, NASA has revealed updated information about its upcoming journey through the solar system.

3I/ATLAS is currently around 4.5 times as far from the sun as Earth is. It will reach its closest point to the sun, or perihelion, on Oct. 30, coming within 1.4 Earth-sun distances, or astronomical units (AU), of our home star. Shortly before this happens, the comet will also make its closest approach to Mars, coming within 0.4 AU of the Red Planet.

Earth will be on the opposite side of the sun to 3I/ATLAS during its solar flyby. The comet will likely make its closest approach to Earth in December, on its journey back out of the solar system. As a result, "the comet poses no threat to Earth and will remain at a [minimum] distance of at least 1.6 astronomical units," NASA officials wrote in the statement.

The interloper is currently too faint to see with amateur stargazing equipment, but it may brighten significantly in the coming weeks and months. However, you can watch it shoot through the solar system via an upcoming livestream from the Virtual Telescope Project, starting at 6:00 p.m. EST on Thursday (July 3).

3I/ATLAS is now "being investigated by astronomers around the world," NASA officials wrote. Researchers will be able to study it until the end of September, when it will become obscured by the sun's light, and again from December onwards when the comet reemerges from behind our home star.

The interstellar visitor will likely be imaged by the Vera C. Rubin Observatory — the world's most powerful optical telescope, which recently released its first images. Some researchers have also suggested using the James Webb Space Telescope and NASA's Mars rovers to photograph the object as it shoots toward the sun.