Earth may survive the fiery death of the sun, even as our star engulfs the innermost planets, a new study using state-of-the-art models suggests.

The findings offer a potential alternative fate for our planet, which was thought to face certain death as the sun engulfs it in a thermonuclear inferno billions of years from now. As a yellow dwarf star, the sun is expected to have a relatively calm, 10 billion-year life. But in about 5 billion years, it will run out of hydrogen to fuse in its core and begin fusing hydrogen in its shell, causing it to expand enormously into a red giant star and then an even larger "AGB star," before it ultimately dies as a white dwarf.

Now, in a Letter to the Editor published June 19 in the journal Astronomy & Astrophysics, astronomers used stellar evolution models and observed a nearby dying star to reassess Earth's ultimate, potentially fiery fate.

Solar tug of war

When the sun enters its later life stages, Earth will be at the mercy of two competing forces — a fate shared by countless worlds throughout the unimaginably immense span of cosmic time.

As the sun expands to potentially hundreds of times its current size, the increased tidal forces will pull Earth toward our rapidly ballooning, sputtering star. Yet the surging sun will also lose its puffed-up outer layers into space through stellar wind. As it sheds much of its mass and becomes lighter, its gravitational grip will weaken, allowing our planet to escape outward into the depths of the solar system, the models show.

"The fate of Earth depends on a delicate balance between these two effects," Mats Esseldeurs, a doctoral candidate at KU Leuven's Institute of Astronomy in Belgium and first author of the study, said in a statement. "If tidal interactions dominate, Earth is engulfed. If mass loss dominates, Earth escapes to a wider orbit."

Previous research only muddies the issue. Studies have made different assumptions about solar mass loss, tidal forces and planetary interactions that may occur as the inner solar system evolves. As a result, it's uncertain if Earth will survive both of the sun's giant phases before our star shrivels into a tiny-but-dense stellar corpse called a white dwarf.

In a glimmer of hope, astronomers have discovered intact worlds around white dwarfs. On the other hand, some white dwarf systems are littered with the rocky remnants of their destroyed planetary children. So the researchers observed the formerly sunlike, dying giant star L2 Puppis, located 200 light-years away in the "poop deck" constellation Puppis, to glimpse our solar future. L2 Puppis may be losing up to one-millionth of a solar mass per year, according to previous estimates, expelling a dusty disk that's thought to harbor a planet 12 to 16 times the mass of Jupiter.

Additionally, the researchers performed state-of-the-art gravitational calculations "based on the internal structure and dynamics of evolved stars," modeling the orbital evolution of the inner solar system and the sun's lifespan from its infancy to its final phase as a "burned out" white dwarf.

So long, Mercury and Venus

Based on observations of L2 Puppis' mass loss, combined with the updated stellar evolution models, the researchers projected that Earth will survive as it shifts to just outside the expanding sun's radius.

"The largest uncertainty no longer comes from the tidal calculations, but from how much mass the future sun will lose," Esseldeurs said in the statement. "Observations of sun-like giant stars currently point towards Earth's survival, but we need better observations before we can be certain."

But even if Earth survives, our solar system siblings will not be spared; the simulations suggest Mercury and Venus will be engulfed by the hellish blaze of our dying star.

Additional stellar observations and improved models will help elucidate our planet's fate. For example, the European Space Agency's PLATO mission, a space telescope that aims to search for Earth-like planets around sunlike stars, will launch next year. It will likely detect planets around aging stars, thus providing a more accurate account of this potentially doomed population.

See how much you know about the sun with our sun quiz!

Something doesn’t quite add up about the orbits of our solar system’s eight planets and their hundreds of moons, a new study hints.

According to the research — which compared more than 100 simulations of our cosmic neighborhood’s early history — there may have once been two extra giant planets careening around the outer solar system, helping to reshape the orbits of the other planets before ultimately being kicked out into interstellar space.

The infant solar system was constantly being reshuffled. One drastic rearrangement, called the giant planet instability, may have caused the giant planets — Jupiter, Saturn, Uranus and Neptune — to migrate from their initial positions, ending up farther from the sun.

This migration, first proposed in 2005 by astronomers in Nice, France, as a part of the "Nice Model," likely started due to extra-close encounters between the planets and leftover planetary building blocks called planetesimals. Additionally, modifications proposed in 2011 suggested there may have been a fifth giant planet whose gravitational encounters with its neighbors ultimately tossed it out of our cosmic neighborhood.

However, astronomers don't know much about this missing planet. To find out more, the new study "systematically tested the effects of giant-planet close encounters on the orbital stability of their satellites," Matthew Clement, a research scientist at the Johns Hopkins University Applied Physics Laboratory and the study's first author, told Live Science in an email.

Replaying cosmic history

For their analysis, the researchers turned to computer models of the early outer solar system. Each model tracked the trajectories of the giant planets and a thousand planetesimals over 20 million years.

From a previously constructed database of 100,000 of these models, the team identified a smaller subset of 122 simulations with final configurations broadly similar to those of the present-day giant planets. Roughly two-fifths of this subset's simulations started with five giant planets, while the remaining began with six. Then, the team "'re-played' these encounter sequences with the giant planets satellites in place," Clement said.

The simulations showed that the extra giant planet (or planets) ping-ponged among their neighbors, before finally being kicked out of the system. But the simulations also revealed an unexpected result: Jupiter's moons remained stable mostly in the simulations with two extra ice giants, while Uranus' moons remained stable in those with just one extra giant planet. In other words, Jupiter's and Uranus' moons appear to have been preserved in separate events ‪—‬ an outcome the researchers found surprising.

The scientists noted that three of Jupiter's big moons — Io, Europa and Ganymede — exist today in an intricate resonance of 1:2:4. In other words, Io completes four orbits of Jupiter for every two of Europa and one of Ganymede. Such a delicately balanced dance suggests that Jupiter's moons have remained largely untouched since they formed and thus favors the existence of two extra ice giant planets, the researchers said.

Planet ping-pong

While ping-ponging between the gas giants and Uranus, these supplemental planets likely destabilized Uranus' moons, causing them to collide. Such collisions would have at least partially fragmented the moons and vaporized volatile materials like ice, which later accumulated on the remnants, possibly explaining why Uranus' moon Miranda has 50% more ice than the planet's other moons, the researchers suggested.

But this isn't the only possibility. Two simulations yielded a scenario resembling the present-day solar system, in which both Jupiter's and Uranus' satellites survived the same instability. In those cases, only one extra ice giant planet was involved. Therefore, further simulations will be needed to discern whether there was one extra ice giant or two, the researchers said in the study.

Little can be inferred about the now-missing planets, except for their masses. In the five-giant-planet scenarios, the one extra planet had a mass similar to that of Neptune, while in the six-planet cases, the two extra planets had masses between those of Earth and Neptune, making them "super-Earths."

"Given that the masses are not too different from Uranus and Neptune, [the long-lost planets'] physical properties probably resembled those planets," study co-author Nathan Kaib, a senior scientist at the Planetary Science Institute in Tucson, Arizona, told Live Science by email.

Although the researchers aren't planning to actively research the fugitive planets, they will continue studying Uranus' moons to identify signatures that show they were disrupted and to determine "the actual consequences of what happens if the satellites do go unstable," Clement said.

The team’s research was published online March 25 in the journal Icarus.

See how well you know our planetary neighborhood with our solar system quiz!

Jupiter's giant moon Ganymede is the only known moon to have its own magnetic field — and it may be heating up in a process "not yet observed anywhere else," new research suggests.

One of the four Galilean satellites swirling around Jupiter, Ganymede is the largest moon in the solar system. At nearly 3,300 miles (5,300 kilometers) in diameter, it's more than 1,000 miles (1,600 km) wider than Earth's moon and slightly bigger than Mercury, our tiniest planetary tot. (Jupiter has more than 100 confirmed moons, with the largest four known as the Galilean moons.)

This standout satellite's intrinsic magnetic field — discovered by NASA's Galileo spacecraft in 1996 — is generated through a process called a dynamo, powered by the electrically conductive, churning liquid iron in its core.

Yet the mechanism through which this process emerged is hotly debated.

"Many formation studies suggest that Ganymede formed too cold to start with a metal core," study co-author Kevin Trinh, a planetary scientist at Caltech, said in a statement. "Meanwhile, many modeling studies of Ganymede's dynamo assume that Ganymede formed its metal core roughly when the moon itself formed, as Earth did. Both of these things cannot be simultaneously true."

So, in a paper published May 6 in the journal Science Advances, researchers propose a new topsy-turvy mechanism that may have formed Ganymede's mysterious metallic core and dynamo later rather than earlier, as molten iron blobs sank into the massive moon's core. This activity may be ongoing today.

Hot or cold start?

The "warming-driven dynamo" presented in the study is the opposite of traditional dynamo-origin ideas, which propose that they form early in large bodies like Earth and then gradually cool.

For example, metallic core formation in planetary bodies is thought to have occurred within around 200 million years of the solar system's formation. Yet moons may be too small to hold enough heat from their birth to power this process.

But all hope is not lost, because a body formed from a "cold start" may still be able to grow a magnetic-field-generating core, the researchers' new model suggests.

This model integrates and simplifies Ganymede's characteristics, such as its composition and core temperature, assuming its core is composed of iron and iron sulfide, because these components have lower melting temperatures.

In this model, molten metal blobs sink into Ganymede's innards to feed its core and whip up its magnetic field. They are warmed through two main mechanisms: radioactive heating and tidal heating.

First, as heavier radioactive isotopes decay into lighter elements, they release heat. Second, Jupiter's gigantic gravitational influence squeezes and stretches Ganymede as the moon whirls nearer and farther from its parent, as if "kneading" a planet-size piece of rocky, icy dough. The resulting inner friction generates heat. This heat powers the dynamo that gives Ganymede its magnetic field.

Altogether, this hypothesis does not preclude the possibility that Ganymede formed with a magnetic-field-producing core.

Alien implications?

But if "cold start" cores exist throughout the universe, it could present a previously unexplored process for magnetic fields to form and protect aging worlds, perhaps facilitating an intriguing implication in the search for extraterrestrial life.

Magnetic fields are necessary to protect life from harmful solar and cosmic radiation, making them a prerequisite in most searches for habitable planets. But a little magnetism can go a long way: As is apparent on Earth, with a magnetic field significantly weaker than a fridge magnet, even a modest magnetosphere can transform the outlook of planetary bodies.

"There could be young rocky exoplanets or exoplanets with lower radioactive isotope abundances (i.e., slower heating) that would be favorable for a recent warming-driven dynamo," Trinh told Live Science in an email. "The challenge is that no one has detected an exoplanet dynamo so far."

The sun has been Earth's constant companion ever since our planet emerged. But if the sun were to suddenly disappear, what would happen to our home planet?

To understand the fate of a sunless Earth, it's important to know how both arose. The sun formed about 4.6 billion years ago, when a massive spinning cloud of gas and dust collapsed in on itself and condensed, creating the biggest object in what would become our solar system and eventually reaching a temperature of 27 million degrees Fahrenheit (15 million degrees Celsius) at its core.

Much of the remaining material nearby then clumped up to form Earth and the other rocky planets, including Mercury, Venus and Mars, as well as moons and asteroids. Since its formation, Earth has been heavily reliant on its star. The sun's gravitational pull keeps our planet in orbit in the "Goldilocks zone," the just-right distance from its star where it's not too hot or too cold for water to exist as a liquid on a planet's surface. The sun also drives photosynthesis and water cycles, and it provides sunlight and heat, which influence our climate. Plus, the sun's ultraviolet light helps our bodies make vitamin D, which is needed for healthy bones and teeth.

If the sun suddenly vanished, Earth and the vast majority of life would be in dire straits. It would start "a ticking time bomb on the survival of every living thing on earth that relies on photosynthesis, which is the vast majority of surface life and all of humanity," Timothy Cronin, an associate professor of atmospheric science at MIT, told Live Science over email.

For at least 8 minutes, 20 seconds, no one would know the sun went missing ‪—‬ that's how long it takes light from the sun to reach Earth. During that time, "we'd almost certainly have no idea that anything had happened," Cronin said.

Then, the real trouble would begin.

After the sun's eight-minute swan song, there would be "a sudden blackout," Cronin said. Without sunlight, artificial lighting from electricity, oil or gas would be the main ways we could still generate light, along with fire, bioluminescence and fluorescence. We'd lose track of day and night. The moon, which reflects the sun's light, would go completely dark, although distant stars in the sky would still be visible. And without the sun's mass and gravity keeping the planets and other celestial bodies in orbit, "all the planets would fly off in the direction of their current travel," Cronin said.

But humanity would have more immediate problems than flying off into interstellar space. No sunlight would mean crucial processes, such as growing food, would become much more complicated.

Photosynthetic organisms would be done for, Michael Summers, a professor of planetary sciences and astronomy at George Mason University in Virginia, told Live Science. Most plants that weren't grown under artificial lighting would quickly suffer. And while some "might stay dormant for weeks to months, like they do in the wintertime, eventually all photosynthetic organisms would die."

Fungi, meanwhile, feed on living or dead matter, and "there would be a great deal of dead material available," Summers said. So fungi likely wouldn't die from a lack of food, but from the cold.

Cold planet

It wouldn't take long for frigid temperatures to change the Earth as we know it.

At first, Earth would cool by an average of roughly 36 F (20 C) every 24-hour period, Summers said. "That plunges almost the whole world into subfreezing temperatures within just two to three days," although as it got colder, the temperature change per day would decrease, he said. Small ponds might freeze over within a week, whereas lakes might take weeks or months. The oceans could persist "for many years, maybe decades," and in certain places, like "the deepest parts of the oceans where you have volcanoes, they might stay liquid for potentially as long as the volcanoes last," Summers said. "And that could be billions of years."

To understand how cold Earth would ultimately get, let's consider Pluto. Right now, Pluto is "about 40 times as far from the sun as Earth is, and the temperature there now is about minus 400 degrees Fahrenheit [minus 240 C]," Summers said. "Once you eject the Earth out of our solar system, it's going to get much further away than Pluto very quickly."

But Earth's temperature wouldn't reach absolute zero, thanks to the Big Bang that happened around 13.8 billion years ago. Even "the lowest temperatures in the universe are limited by heat that's left over from the Big Bang," Summers said. "Take any object very far away from a star and let it cool for a million years," and it will still remain a few degrees above absolute zero. The temperature of the leftover radiation known as the cosmic microwave background is about minus 454 F (minus 270 C), whereas absolute zero is slightly chillier at about minus 459 F (minus 273 C).

At an ultracold temperature, human civilization and most of life would almost certainly collapse. "It's conceivable that people could survive underground in caves, sustained by geothermal or nuclear energy, with plants grown under artificial lighting," Cronin said, "but this would be an extinction event to make all others look puny."

What would survive?

One thing that might survive? Near-microscopic animals called tardigrades, also known as water bears. "Ugly little critters," Summers said, but "hard to kill." They can be zapped with radiation or immersed in certain types of alcohol and still survive; perhaps hitting them with a hammer would kill them, he suggested. "Otherwise, they're pretty much one of the hardiest forms of life on Earth."

Likewise, bacteria that don't require photosynthesis, such as types that live around deep ocean vents, would likely survive. That's because certain microbes, including some bacteria and archaea, use chemosynthesis, as opposed to photosynthesis, to "live off of chemical bonds in rocks and minerals," Summers added.

Fortunately for humanity, there is no reason to believe the sun will vanish in the blink of an eye. Over time, however, the sun will die. It will continue to create heat and light for another 5 billion years or so, but once its fuel runs out, it will expand into a red giant, swallowing Mercury and Venus and perhaps Earth. Regardless, humans likely won't last that long; the sun's gradual increase in brightness is expected to vaporize Earth's oceans in a little over a billion years from now.

While those impacts may be a long way away, Summers said it's important to consider the potential outcomes. When "we understand more about stars and how they can change over time, on short timescales and on long timescales, we understand the universe better."

Sun quiz: How well do you know our home star?

Scientists using the James Webb Space Telescope just mapped the mysterious upper atmosphere of Uranus for the first time, revealing strange new features of the planet's mysterious magnetic field and glowing auroras.

The James Webb Space Telescope (JWST) observed Uranus rotating for 15 hours (nearly a full Uranian day) to learn more about how ice giants distribute energy in the upper layers of their atmospheres and to investigate how the planet's auroras operate.

Uranus' magnetic field is unique among the big planets of our solar system in that its magnetic pole is tilted by 60 degrees relative to its geographic pole. That tilt produces auroras that extend far beyond the poles of Uranus, unlike auroras on Earth.

To learn more, scientists used JWST to study Uranus' magnetosphere — the region of space around Uranus that's dominated by the planet's magnetic field.

"Uranus's magnetosphere is one of the strangest in the solar system," study lead author Paola Tiranti, a doctoral student at Northumbria University in the U.K., said in a European Space Agency (ESA) statement. "Webb has now shown us how deeply those effects reach into the atmosphere."

Strange lights on Uranus

JWST charted "the most detailed portrait yet" of how particles in Uranus' upper atmosphere are energized (ionized) by interactions with the sun, ESA officials said in the statement. The study, published Feb. 19 in the journal Geophysical Research Letters, aimed to measure ion temperature and density as far as 3,100 miles (5,000 kilometers) above the cloud tops of Uranus.

Temperature and density do not peak at the same altitude, JWST showed. Ions were the warmest between roughly 2,500 and 3,100 miles (4,000 and 5,000 km) but the densest at about 600 miles (1,000 km). This is because of the "complex geometry" of the planet's magnetic field, ESA officials said in the statement.

That geometry also produced two bright bands of auroras near Uranus' magnetic poles. In between the aurora belts, however, there is a "depletion" in both ion density and auroral emissions — an effect likely produced by transitions between the planet's magnetic-field lines, the scientists said. Observations at Jupiter's upper atmosphere have shown similar transition regions.

In addition to charting Uranus' upper atmosphere in three dimensions for the first time, JWST confirmed findings from previous studies that suggested the planet's upper atmosphere has been cooling steadily since the early 1990s. The telescope showed the average temperature of Uranus' atmosphere is about 307 degrees Fahrenheit (153 degrees Celsius), which is lower than the temperature measurements from other spacecraft and ground-based telescopes.

"By revealing Uranus's vertical structure in such detail, Webb is helping us understand the energy balance of the ice giants," Tiranti said. "This is a crucial step towards characterizing giant planets beyond our solar system."

James Webb Space Telescope quiz: How well do you know the world's most powerful telescope?

Astronomers have spotted an unusual planetary system with a rebellious rocky planet orbiting well beyond where it would be expected to form.

Typically, rocky planets develop closer to a star, and gaseous planets form farther out — as is the case in our solar system, with a vast asteroid belt drawing the line between rocky Mars and gassy Jupiter.

And in the newly spotted system of four planets, the first three follow this pattern. But the system also has a rocky planet orbiting at its outer edge, beyond the two gas planets. That suggests the planet formed after the gas in the protoplanetary disk was already used up, researchers reported Feb. 12 in the journal Science.

"This strange disorder makes it a unique inside-out system," study co-author Thomas Wilson, an exoplanet scientist at the University of Warwick in the U.K., said in a statement. "Rocky planets don't usually form far away from their home star, on the outside of the gaseous worlds."

A rebel world

As the planets in our solar system formed and grew, they accreted dust, metals and other solids. Far from the sun, materials such as water and methane remained solid due to the cooler temperatures. As the outer planets got larger, they pulled in hydrogen and helium from their surroundings and grew into gas giants.

"Historically, our planet formation theories are based on what we see and know about our Solar System," study co-author Isabel Rebollido, a researcher who studies exoplanet systems at the European Space Agency (ESA), said in the statement. "As we are seeing more and more different exoplanet systems, we are starting to revisit these theories."

In the new study, Wilson and colleagues searched for exoplanets surrounding the red dwarf star LHS 1903, which had been observed by the Transiting Exoplanet Survey Satellite between 2019 and 2023. When a planet passes between the star and the satellite, it dims the star's light slightly. Then, they studied the properties of those planets, using the Characterizing Exoplanets Satellite (CHEOPS).

The scientists spotted four exoplanets orbiting the star, including the distant rocky one. The planets likely did not form at the same time, the team found; instead, they developed one by one and changed the environment in which each subsequent planet grew.

"By the time this final outer planet formed, the system may have already run out of gas, which is considered vital for planet formation," Wilson said in the statement. "Yet here is a small, rocky world, defying expectations. It seems that we have found [the] first evidence for a planet that formed in a gas-depleted environment."

The team further ruled out ideas that the distant rocky planet had lost its atmosphere in a collision or swapped places with a gas planet.

"Much about how planets form and evolve is still a mystery," study co-author Maximilian Günther, an astrophysicist at ESA, said in the statement. "Finding clues like this one for solving this puzzle is precisely what CHEOPS set out to do."

New evidence of ancient rivers suggests Mars may have been a "blue planet," thanks to an ocean spanning its entire northern hemisphere.

Cameras from several Mars orbiters captured the dusty remnants of apparent river deltas, which were described in research published Jan. 7 in the journal NPJ Space Exploration.

The team, led by researchers at the University of Bern, peered at the famed Valles Marineris, which is the largest valley system on Mars and five times longer than the Grand Canyon. Around this Red Planet region, scientists spotted "structures near the canyon system that resemble river deltas on Earth," University of Bern representatives wrote in a statement.

"These structures represent the mouth of a river into an ocean," the statement added. "The new study thus provides clear evidence of a coastline, and consequently, of an earlier ocean on Mars."

Water, water everywhere

Although Mars is dry and dusty today, there are many signs that the planet hosted water in the ancient past. For example, Mars rovers have spotted "blueberry stones" that may include iron oxide minerals containing water. NASA's Curiosity rover imaged possible "ripples" of an ancient riverbed in 2025, and some orbital missions have spotted what may be vast underground stores of water.

The new study focused on Martian geomorphology — the study of the surface and its processes — and employed several spacecraft, including the ExoMars Trace Gas Orbiter, Mars Express and the Mars Reconnaissance Orbiter (which recently shared its 100,000th photo).

"The unique high-resolution satellite images of Mars have enabled us to study the Martian landscape in great detail by surveying and mapping," Ignatius Argadestya, lead author of the study and a doctoral student at the University of Bern Institute of Geological Sciences as well as the university’s Physics Institute, said in the statement.

"When measuring and mapping the Martian images, I was able to recognize mountains and valleys that resemble a mountainous landscape on Earth," Argadestya said. "However, I was particularly impressed by the deltas that I discovered at the edge of one of the mountains."

The team saw possible "fan deltas," which form when debris and sand pile up in still water. The deposits in the Martian imagery appear very similar to active fan deltas on Earth, according to the team; on our planet, these deltas pile up at entry points where rivers flow into the ocean.

All of the "deposits" were mapped at an elevation of between 11,975 and 12,300 feet (3,650 to 3,750 meters) and formed roughly 3.37 billion years ago. Given that all of the deposits are at roughly the same elevation and in a region in the northern lowlands of Mars and Valles Marineris, the researchers argue that these structures mark the boundaries of an ancient shoreline. It's likely the ocean that once flowed there spanned Mars' entire northern hemisphere, the team added.

In part drawing on past research, the scientists say this ancient Martian ocean was at least as large as the present-day Arctic Ocean.

"We are not the first to postulate the existence and size of the ocean," Fritz Schlunegger, a geology professor at the University of Bern and co-author of the study, said in the statement. "However, earlier claims were based on less precise data and partly on indirect arguments. Our reconstruction of the sea level, on the other hand, is based on clear evidence for such a coastline, as we were able to use high-resolution images."

This weekend brings a prime opportunity to see the biggest planet in the solar system shining at its brightest all year.

After dominating the night sky for more than a month, Jupiter will reach opposition this Saturday (Jan. 10). This marks the point when Earth lies directly between Jupiter and the sun, putting the gas giant opposite our star in Earth's sky. The result is a brilliant, unmissable light in the eastern evening sky that shines all night long. At magnitude -2.7, Jupiter will outshine every star for many weeks.

(In astronomy, a lower magnitude corresponds to a brighter object. Sirius, the brightest star in the night sky, has an apparent magnitude of about -1.4.)

Shining in the constellation Gemini near the bright stars Pollux and Castor, Jupiter's opposition is the best time to see the giant planet because it rises at sunset, climbs highest around midnight, and sets at dawn. It's a prime opportunity for both novice and experienced skywatchers to get an extraordinary look at the "king of the planets."

How to see Jupiter and its moons

To marvel at Jupiter's dominance at night, you'll need nothing more than a clear sky. However, even a modest pair of binoculars (8×42 or 10×50) will reveal Jupiter as more than just a bright dot; you'll see a small, steady disk and the planet's four largest moons: Io, Europa, Ganymede and Callisto. Known as the Galilean moons, they appear as tiny points of light lined up beside the planet, changing position each night.

With a small telescope, the view becomes even more impressive. Use a low-power eyepiece to center Jupiter in your field of view, and then switch to a higher magnification. Two or more dark cloud bands should be visible crossing the planet's disk — signs of Jupiter's powerful jet streams. Under steady atmospheric conditions, the famous Great Red Spot — a massive storm that's been raging on Jupiter for around 190 years — also may come into view in the planet's southern hemisphere.

While Jupiter steals the show, Saturn is also visible in the early evening sky, hanging lower in the southwest after sunset. Though fainter, its iconic rings are still visible through a telescope — a treat for any observer.

Jupiter will remain well placed for evening viewing throughout January and into February. It's an ideal time to observe it under dark skies, before it gradually shifts westward in the coming months.

Jupiter won't disappear after opposition. On June 9, it will form a striking triple conjunction with Venus and Mercury in the twilight sky. Then, on Nov. 15, it meets Mars in a spectacular close conjunction just before sunrise.

The next opposition of Jupiter will occur on Feb. 6, 2027.

The interiors of Uranus and Neptune may be rockier than scientists previously thought, a new computational model suggests — challenging the idea that the planets should be called "ice giants."

The new study, published Dec. 10 in the journal Astronomy & Astrophysics, may also help to explain the planets' puzzling magnetic fields.

Uranus and Neptune are relatively large planets at the edge of the solar system; Neptune is the most distant planet, orbiting at 2.8 billion miles (4.5 billion kilometers) from the sun, on average. The extremely cold temperatures at these distances cause gases such as hydrogen, helium and water to condense into compressed ice slurries that form the planets' cores. As such, these planets have become known as ice giants.

"The ice giant classification is oversimplified as Uranus and Neptune are still poorly understood," lead study author Luca Morf, a doctoral student at the University of Zurich, said in a statement.

Far out planets

Morf and his supervisor, Ravit Helled, developed a new hybrid model in an attempt to better understand the interior of these cold planets. Models based on physics alone rely heavily on assumptions made by the modeler, while observational models can be too simplistic, Morf explained. "We combined both approaches to get interior models that are both unbiased and physically consistent," he said.

The pair started by considering how the density of each planet's core could vary with distance from the center of the planets and then adjusted the model to account for the planets' gravities. From this, they inferred the temperature and composition of the core and generated a new density profile. The team inputted the new density parameters back into the model and iterated this process until the model core fully matched current observational data.

This method generated eight total possible cores for both Uranus and Neptune, three of which had high rock-to-water ratios. This shows that the interiors of Uranus and Neptune are not limited to ice, as previously thought, the researchers said.

All of the modeled cores had convective regions where pure water exists in its ionic phase. This is where extreme temperatures and pressures cause water molecules to break apart into charged protons (H⁺) and hydroxide ions (OH^-). The team thinks such layers may be the source of the planets' multiple magnetic fields, which cause Uranus and Neptune to have more than two poles. The model also suggests that Uranus' magnetic field is generated closer to its center than Neptune's is.

"One of the main issues is that physicists still barely understand how materials behave under the exotic conditions of [high] pressure and temperature found at the heart of a planet [and] this could impact our results," Morf said. The team aims to improve their model by including other molecules, like methane and ammonia, which also may be found in the cores.

"Both Uranus and Neptune could be rock giants or ice giants depending on the model assumptions," Helled said. She noted that much of our understanding of these planets may be incomplete, as it's based largely on data collected by the Voyager 2 space probe in the 1980s.

"Current data is insufficient to distinguish the two, and we therefore need dedicated missions to Uranus and Neptune that can reveal their true nature," Helled added

The team hopes the model may act as an unbiased tool for any new data from future space missions to these planets.

If you peer at the sky during a cloudless dawn or dusk, you'd immediately spot Venus. Appearing as a brilliant, steadily shining speck, it's the second-brightest object in the night sky after the moon.

"The planet is about 100 times brighter than a first magnitude star," Anthony Mallama, a researcher at the IAU's Centre for Protection of the Dark and Quiet Sky, told Live Science in an email. First magnitude stars are the brightest stars visible in the night sky. For example, when looking at average brightness, the first magnitude star Sirius is at -1.47, and Venus is at -4.14 (on the scale astronomers use, dimmer objects have a more positive magnitude).

But what makes Venus super-bright? Astronomical research suggests several factors can change how luminous Venus appears from Earth.

Reflective cloud cover

Venus' shininess is largely due to the planet's high albedo, or the amount of light reflected off its surface. Venus has an albedo of 0.76, meaning it scatters about 76% of the sunlight it receives back into space, according to Sanjay Limaye, a distinguished scientist in the Space Science and Engineering Center at the University of Wisconsin-Madison. In contrast, a perfect mirror would bounce off 100%, Earth bounces 30% and the moon has a low albedo, reflecting just 7% of the light that hits it.

Venus' high albedo arises from a thick, all-swaddling cloak of clouds. Extending from 30 miles to 43.5 miles (48 to 70 kilometers) above the Venusian surface, these decks of clouds are cushioned between haze layers, and are mostly suspended droplets of sulfuric acid, according to a 2018 review of data from 1970s and 1980s space missions to Venus. Limaye noted that such droplets are tiny, mostly about the size of a bacterium. Together, the droplets and haze layers scatter sunlight extremely efficiently.

But Venus isn't the solar system's shiniest object. Saturn's ice-covered moon Enceladus has a high albedo of around 0.8, a 2010 study noted. From Earth, though, this cosmic object appears much dimmer than Venus. That's because it's much farther from the sun. While Earth's "morning star" is 67 million miles (108 million km) from the sun, Enceladus is at least 13 times as distant. The inverse square law shows that Venus consequently receives 176 times more intense light compared to Enceladus, giving it a significant edge.

Distance from Earth

Being close to Earth also influences Venus' brightness. The average Venus-Earth distance is 105.6 million miles (170 million km). Sometimes, Mercury is the closest planet to Earth at an average distance of 96.6 million miles (155.5 million km), but Venus' larger size (of 7,521 miles (12,104 km) compared to Mercury causes it to look brighter.

But Venus' distance from our planet — and consequently, its apparent luminosity — aren't fixed. At its closest, when Venus lies directly between Earth and the sun, it's a mere 24 million miles (about 38 million km) away, according to NASA. Yet at this point — called the inferior conjunction — it's actually extremely dim, according to the National Astronomical Observatory of Japan.

This arises because the inner planets show moon-like phases when viewed from Earth, Limaye said. At inferior conjunction, Venus' illuminated surface is completely invisible from Earth. In contrast, most of Venus' illuminated surface can be seen only when Earth and Venus are on opposite sides of the sun, a position called the superior conjunction. At this point, though, Venus is at its smallest and is very dim because it is extremely far from Earth.

A rainbow-like phenomenon

Venus is at its brightest when only a crescent-like sliver of its sunlit surface can be seen. Termed the point of greatest brilliancy, this typically occurs a month before and after the inferior conjunction. A 2006 study co-authored by Mallama suggested that, at this phase, Venus' suspended sulfuric acid droplets scatter sunlight toward Earth. "This phenomenon is called a glory and it is in the same family of optical effects that includes rainbows," Mallama explained.

Together, variations in the albedo, its distance from the Earth and sun, and its phases seen from Earth can all cause the brightness of Venus to swing from -4.92 to -2.98, according to a 2018 study. However this is still luminous enough to make Venus viewable most of the year, even from urban areas.

Solar system quiz: How well do you know our cosmic neighborhood?

Roughly 4.5 million years ago, the sun passed remarkably close to two intensely bright stars whose radiation flooded nearby space — and the encounter left a ghostly scar that astronomers can still detect today, according to a new study.

The research team says the close pass helps to solve a decades-old mystery of why the space around our solar system is far more energized than models predict, including why it contains a surplus of ionized helium.

Using computer models to rewind the paths of stars near the sun, a team led by University of Colorado Boulder astrophysicist Michael Shull found that two blue-white stars, Beta Canis Majoris and Epsilon Canis Majoris, passed within 30 light-years of the sun about 4.5 million years ago.

Today, the stars mark the front and rear legs of the constellation Canis Major (the Great Dog), more than 400 light-years from the solar system. But roughly 4.5 million years ago, when the stars brushed past the solar system, they were younger, hotter and brighter. Their passage also may have overlapped with the time when Lucy — a remarkably complete fossil of an early human ancestor discovered in Ethiopia in 1974 — walked the Earth.

"They weren't headed straight toward us...but that's close," Shull told Live Science. "If Lucy and her friends had looked up and had noticed the stars, the two brightest stars in the sky would have been not Sirius, but Beta and Epsilon Canis Majoris."

The findings were published Nov. 24 in The Astrophysical Journal.

A lingering mystery

Today, the solar system drifts through a diffuse patchwork of more than a dozen nearby wisps of gas and dust called the local interstellar medium, made primarily of hydrogen and helium and extending roughly 30 light-years from the sun.

Astronomers think these clouds were sculpted over several million years by shock waves from exploding stars in the Scorpius-Ophiuchus region, a rich cluster of massive stars about 300 light-years from Earth, which compressed interstellar gas into the thin local clouds seen today.

Observations dating back to the 1990s, including from NASA's now-retired Extreme Ultraviolet Explorer space telescope, revealed that this region is unusually ionized. Helium atoms, in particular, have been stripped of their electrons at nearly twice the rate expected relative to hydrogen.

That imbalance has puzzled astronomers, because helium requires more energetic radiation to ionize than hydrogen does. This makes its elevated ionization difficult to explain with the sun's radiation alone, which does not extend that far beyond the solar system.

To investigate the mystery, Shull and his colleagues calculated the properties and ultraviolet output of Beta and Epsilon Canis Majoris, using measurements from the European Space Agency's Hipparcos satellite, which mapped the positions of more than a million stars across a four-year mission that ended in 1993.

Knowing how far away the two stars are today — about 400 light-years — and how fast they are moving allowed the team to trace the stars' paths backward through time to reconstruct their close pass by the solar system roughly 4.5 million years ago.

"It's like a dance floor"

The team's models show that the wispy local clouds would have been intensely ionized by the two stars' radiation — at levels up to 100 times stronger than those seen today. Over time, the gas would have slowly returned to a more neutral state through a process called recombination, in which free electrons reattach to ions and become atoms.

"It's like a dance floor," Shull told Live Science. "You've got protons and electrons dancing around, and sometimes they're dancing together and sometimes they're popping apart."

But that process takes time, and continued exposure to radiation from other sources continues to keep the gas partially ionized, Shull said. Astronomers had previously identified other sources of ionizing radiation, including three nearby white dwarf stars — G191-B2B, Feige 24 and HZ 43A — compact stellar remnants that are known to emit strong ultraviolet light. Researchers also pointed to the Local Bubble — a vast, supernova-blown region of hot gas that extends about 1,000 light-years around the solar system.

"More energetic photons preferentially ionized helium," he said. "That's the bottom line."

The pieces come together

Although astronomers have had reliable stellar motion data for decades, Shull said the problem became solvable only recently. Advances in ultraviolet and X-ray observations made possible by suborbital rocket flights, along with improved models of stellar evolution and atmospheres — and the computing power needed to run them — finally allowed researchers to connect the dots.

"The problem was ripe in the sense that all the pieces of the puzzle of the mystery were starting to come together," Shull said.

The findings also may have implications closer to home. The local clouds help shield the planet from high-energy particles that roam the galaxy and that scientists suspect could erode Earth's ozone layer.

The sun, however, is not expected to remain inside these clouds indefinitely. As it drifts onward through the galaxy, researchers estimate it could exit the protective region in as few as 2,000 to a few tens of thousands of years. "Then, we're going to be in for a big dose of radiation," Shull said.

Looking ahead, Shull said that understanding how atoms in the wispy local clouds shifted between more charged and more neutral states as radiation waxed and waned while the two stars approached, passed by and moved away from our solar system remains part of a larger puzzle researchers are still assembling. "The problem isn't completely solved," Shull said, "but I think we have the right track."

The catastrophic collision that forged the moon, and marked one of the most consequential events in Earth's early history, may have been triggered not by a distant interloper, but by a sibling world that grew up right next door, according to a new study.

About 4.5 billion years ago, a Mars-size world slammed into the young Earth with such tremendous force that it melted huge swaths of our planet's mantle and blasted a disk of molten debris into orbit. That wreckage eventually clumped together to form the moon we know today. Scientists have long favored this "giant impact" origin story, but where the long-lost world, nicknamed Theia, came from and what it was made of remain a mystery.

But the new analysis of moon samples from Apollo missions, terrestrial rocks and meteorites now argues that Theia, much like Earth, was a rocky world that formed in the inner solar system — likely even closer to the sun than our planet.

"Theia and proto-Earth come from a similar region of the inner solar system," Timo Hopp, a geoscientist at the Max Planck Institute for Solar System Research in Germany, who led the research, told Live Science.

The findings, detailed in a paper published Nov. 20 in the journal Science, reinforce the classical picture of how rocky planets assembled billions of years ago, Hopp said.

"Our results do not predict a new twist in the mechanism," Hopp said. Instead, they "are in very good agreement from what we expect from the classical theory of terrestrial planet formation."

Violent youth of the planets

In the turbulent first 100 million years after the sun formed, the inner solar system was crowded with dozens to hundreds of planetary embryos — moon- to Mars-size worlds that frequently collided, merged or were kicked into new orbits by the gravitational chaos of early planet formation, as well as by Jupiter's immense pull.

"Theia was one of 10-100s of planetary embryos from which our planets formed," said Hopp. But lunar samples from the Apollo missions have shown that Earth and moon are nearly chemically identical, a similarity that scientists say has made pinpointing Theia's birthplace extremely difficult.

To investigate, Hopp and his colleagues searched for minuscule chemical clues left behind from the impact in Earth's mantle — traces of elements such as iron and molybdenum that should have sunk into Earth's core if they had been present early in the planet's formation. Their survival in mantle rocks today suggests these elements arrived later, likely delivered by Theia during the giant impact, and therefore carry valuable information about the lost planet's composition, the researchers say.

Clues from the moon

The researchers analyzed six lunar samples from the Apollo 12 and 17 missions alongside 15 terrestrial rocks that included specimens from Hawaii's Kīlauea volcano, as well as meteorites recovered from Antarctica and curated in major museum collections.

The team focused on extremely subtle differences in iron isotopes (different versions of elements), which recent research shows can pinpoint where material formed relative to the sun. They combined these iron measurements with isotopic signatures of molybdenum and zirconium, then compared the results with known meteorite compositions to deduce which kinds of planetary "building blocks" could have formed Theia.

Across hundreds of modeled scenarios, from small impactors to bodies nearly half the mass of Earth, the only configuration that successfully reproduced the chemistry of Earth and the moon was the one in which Theia formed in the inner solar system, the study reports. Theia was likely a rocky, metal-cored world containing roughly 5 to 10% of Earth's mass, the team notes.

The models also reveal that both proto-Earth and Theia contain material from an "unsampled" inner-solar-system reservoir, a type of matter absent from all known meteorite collections. This mysterious component likely formed extremely close to the sun, in a region where early material was either swept up by Mercury, Venus, Earth and Theia — or never survived as free-floating bodies capable of becoming meteorites.

"It might be only sample bias," Hopp acknowledged. Samples from Venus or Mercury, he added, may someday reveal larger fractions of this missing material and could ultimately "confirm or reject our conclusion."

While the study clarifies that Earth and Theia were likely local siblings, how the giant impact mixed the two worlds so thoroughly that their chemical identities became nearly indistinguishable remains an open question, Hopp said.

Cracking that mystery may reveal the last missing chapter in the moon's violent origin story — and could be the key to fully understanding how our moon and Earth came to be.

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.

NASA's Perseverance rover has discovered a highly unusual rock lying on the surface of Mars. The lumpy boulder, which has a metal-rich composition, is most likely a meteorite that crash-landed on the Red Planet — and it's the first one that Perseverance has found during its four-year mission scouring Mars rocks for signs of life.

Perseverance has found many different rocks since landing within Mars' Jezero crater in early 2021, including a "spider-egg" rock, an out-of-place "skull" and, most recently, a bizarre "turtle-shaped" formation. Some of these rocks have also yielded surprising results, such as strange nodules recently found in organic-rich samples, which could be the "clearest sign" yet of past extraterrestrial life on Mars.

Until now, the one thing that all the rocks surveyed by Perseverance had in common was that they originated on Mars. But on Sept. 19, during the 1,629th Sol (Martian day) of the rover's mission, the wandering robot came across an odd-looking boulder while exploring an area of Jezero dubbed "Vernodden." The unusual rock, which measures around 31 inches (80 centimeters) across, has since been named "Phippsaksla" — and is unlikely to have a Martian origin.

"This rock was identified as a target of interest based on its sculpted, high-standing appearance that differed from that of the low-lying, flat and fragmented surrounding rocks," Candice Bedford, a geochemist and mineralogist at Purdue University's Planetary Science department, wrote in a NASA statement.

Analysis of the rock revealed it has a high concentration of iron and nickel, which is unusual in Martian rocks. But these metals are commonly found in meteorites, "suggesting that this rock formed elsewhere in the solar system," Bedford wrote. It is unclear how long it has been on Mars, but it is likely millions, if not billions, of years old.

"This is not the first time a rover has encountered an exotic rock on Mars," Bedford wrote. In fact, three different NASA rovers — Spirit, Opportunity and Curiosity — have found potential meteorites during their respective missions, she added. (Of these missions, only Curiosity is still active.)

"As such, it has been somewhat unexpected that Perseverance had not seen iron-nickel meteorites within Jezero crater, particularly given its similar age to Gale crater [where Curiosity currently resides]," Bedford wrote.

Despite finding the potential meteorite roughly two months ago, the discovery has only just been announced due to the recent U.S. government shutdown. The NASA statement about Phippsaksla was originally written on Oct.1, the same day the shutdown began, and was released on Nov. 13, the day after the government reopened.

The shutdown proved to be quite eventful for NASA. Live Science's sister site Space.com recently reported that officials had likely begun implementing the agency's proposed budget cuts during this time, before they had been approved by Congress. And since the shutdown has ended, NASA scientists have been busy sharing previously withheld images of the interstellar comet 3I/ATLAS.

However, Perseverance remained online throughout the entire shutdown along with several other "mission-critical operations."

Martian meteorites

While finding meteorites on Mars is uncommon, here on Earth we have found lots of space rocks that came from Mars.

These Martian meteorites were ejected by other large meteor impacts on Mars, and later fell to Earth after drifting through space for thousands of years. They are highly sought after by scientists because they can tell us a lot about the rocks on Mars, just like Perseverance.

In 2024, one study found that around 200 of the Martian meteorites that have fallen to Earth originated from just five different impact craters on the Red Planet.

And in July, one Martian meteorite — a 54-pound (24.5 kilograms) space rock dubbed NWA 16788, which crashed into the Sahara desert in 2023 — was sold for $5.3 million at auction, which is a new record for a Martian space rock.

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 strange, lopsided dust cloud shrouds Earth's moon, ever skewed toward whichever side is facing the sun. Now, a new study may finally explain how the asymmetrical cloud got its shape.

Most of the moon's surface is covered by a layer of gray dust and loose rocks. This layer, called regolith, arises because the lunar surface is constantly bombarded by micrometeoroids — tiny space rocks created by asteroid collisions and comets. Without a protective atmosphere — which, in Earth's case, causes micrometeoroids to burn up as "shooting stars" — the moon is struck by several tons of micrometeoroids daily. These impacts, in turn, grind the regolith's rocks to dust.

The micrometeoroids also lift lunar dust. In 2015, researchers found that this rising dust creates a massive cloud that extends several hundred miles above the lunar surface. The cloud isn't very thick, and it's not visible to the naked eye, Sébastien Verkercke, a postdoctoral researcher at the Centre National D'Etudes Spatiales (France's national space agency) in Paris and the new study's first author, told Live Science in an email.

"The maximum density measured was only 0.004 particles per cubic meter (the equivalent to 4 dust grains in a grain silo)," he said. However, the cloud is unusual in being asymmetric, with more dust present over the moon's daytime side (the side facing the sun at any given moment) than its nighttime side. In fact, the cloud is "densest close to the surface near the dawn terminator," Verkercke added, referring to the stark line that separates sunlight from darkness on the moon's surface.

The cloud's discoverers had attributed this lopsidedness to specific meteoroid groups with trajectories that cause the meteoroids to strike the daytime surface more frequently. But the obvious difference between the daytime and nighttime sides of the moon — the temperature — stuck out to Verkercke.

Whereas the moon's surface is often broiling during the day, with temperatures soaring far above that of the hottest place on Earth, the lunar night is four times colder than Antarctica's average temperature. This ginormous temperature swing of up to 545 degrees Fahrenheit (285 degrees Celsius) led Verkercke and his co-authors to wonder if it could be responsible for the cloud's skewed appearance.

To test this hypothesis, Verkercke and his colleagues (researchers from U.S. and European universities) turned to computer models. The team simulated tiny meteoroids — each the width of a human hair — slamming into the lunar dust at two temperatures, 233 degrees Fahrenheit (112 degrees Celsius) and minus 297 degrees Fahrenheit (minus 183 degrees Celsius), corresponding to the moon's average daytime and pre-dawn temperatures, respectively.

"The ejected dust grains are then individually tracked to monitor their distribution in space," Verkercke said. The researchers also repeated the simulations while varying how compactly it was packed.

They found that meteoroids that hit "fluffier" surfaces throw up smaller amounts of dust, because the fluffiness of the surface cushions the impacts. In contrast, meteoroids that strike more compact surfaces yield larger amounts of low-speed dust particles. The researchers think this difference means that the dust clouds can be a marker of how compact the lunar surface is.

Moreover, daytime meteoroids raise 6% to 8% more dust than nighttime ones do. And a larger fraction of those dust particles at high temperatures (relative to those formed at lower temperatures) have enough energy to reach the height of orbiting satellites that can detect them. Both the larger amounts of lofted dust and the bigger fractions of dust reaching the satellites could explain the daytime dust excess, the researchers explained in the study, published Oct. 15 in the Journal of Geophysical Research: Planets.

The team plans to extend their analysis to other bodies in the solar system that are impacted by small meteoroids. Verkercke noted that one particularly interesting case is Mercury, which has a much hotter temperature than the moon's daytime surface and thus, a larger day-night temperature difference. This, in turn, should create an even more asymmetrical dust cloud.

The researchers hope to virtually replicate this hypothesized observation, which the BepiColombo mission to Mercury will also investigate, Verkercke added.

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.

Astronomers have discovered a 2,300-foot-wide (700 meters) asteroid hidden in the sun's glare, and it’s whizzing through our solar system at a near record-breaking pace.

The skyscraper-size asteroid, named 2025 SC79, loops around the sun once every 128 days, giving it the second-fastest asteroid orbit in the solar system. It is also only the second known space object that orbits entirely inside of Venus' orbit, occasionally even crossing the orbit of Mercury.

Scott Sheppard, an astronomer at the Carnegie Science research institute in Washington, D.C., first spotted 2025 SC79 on Sep. 27. The asteroid was obscured by the sun's glare, making it exceptionally difficult to observe, according to a statement released by Carnegie Science. Spotting hidden asteroids like 2025 SC79 is important to ensure that no potentially hazardous space rock sneaks up on our planet without us noticing.

"The most dangerous asteroids are the most difficult to detect," Sheppard said in the statement. "Most asteroid research finds these objects in the dark of night, where they are easiest to spot. But asteroids that lurk near the Sun can only be observed during twilight — when the Sun is just about to rise or set. If these 'twilight' asteroids approach Earth, they could pose serious impact hazards."

Asteroids like 2025 SC79 are definitely worth keeping an eye on. To put its 2,300-foot diameter in context, the so-called "city-killer" asteroid 2024 YR4 discovered earlier this year is only around 180 feet (55 meters) wide, and that has the potential to release 500 times more energy than the atomic bomb that destroyed Hiroshima if it were to hit Earth (don't worry, it almost certainly won't).

Sheppard discovered 2025 SC79 using the Dark Energy Camera on the National Science Foundation's (NSF) Blanco 4-meter telescope. The asteroid's existence was then confirmed with observations from the NSF's Gemini telescope and Carnegie Science's Magellan telescopes, according to the statement.

This is the second super speedy asteroid spotted by Sheppard and his colleagues in recent years, having also discovered the fastest known asteroid in 2021. That object, named 2021 PH27, orbits the sun in 113 days, making it just 15 days quicker than 2025 SC79. The only object in the solar system with a faster orbital period is the planet Mercury, which completes an orbit of the sun in 88 days.

2025 SC79's orbit has now taken it behind the sun, so it won't be visible for several months. Researchers will attempt further observations in the future to learn more about the object, which is ultimately another piece of the galactic puzzle that helps astronomers understand how our solar system and its potential asteroid-shaped threats evolved.

"Many of the Solar System's asteroids inhabit one of two belts of space rocks, but perturbations can send objects careening into closer orbits where they can be more challenging to spot," Sheppard said. "Understanding how they arrived at these locations can help us protect our planet and also help us learn more about Solar System history."

About 4.6 billion years ago, a celestial cloud collapsed, paving the way for our solar system to form. Then, a nebula with strong gravitational pull took shape, kick-starting the birth of the sun. But after that, the details leave more room for debate about which planets formed first.

So, what do we know about which planets emerged early, and which ones developed later on?

Despite advanced techniques like dating organic materials from space, going on multiple visits to the moon, and sending rover expeditions to Mars, planetary scientists are still unsure about the ultimate birth order of the planets in the solar system. Beyond the planets' initial formation, there are also several competing theories to explain the order in which the planets came to be.

"It's complex — there are no easy answers to measuring time in outer space," Michael Meyer, chair of the University of Michigan's astronomy department, told Live Science. "It is the most difficult thing to do in astronomy."

The most commonly accepted explanation for how our solar system's eight planets formed is called accretion — when small particles of gas and dust collide and stick to each other, allowing them to gain gravitational pull and grow over time.

One popular theory, which assumes accretion took place, is that the large planets started to form first, far from the sun, according to NASA. As they got bigger, they moved outward, making room for the terrestrial, rocky planets to form. These formations took place closer to the sun and millions of years later (a relatively short time span in astronomical terms).

"In order to form a gas giant planet, you have to have enough gas to make a Jupiter — and that gives us a hard upper limit for how long it can take to form a gas giant," Meyer said. "If you don't get the whole process started fast enough and the gas goes away, then you can't make a gas giant. That's why we think the gas giants formed first."

But a competing theory, called the streaming instability model, offers a different explanation. By allowing planets to gather mass more spontaneously, this theory could allow an entirely different sequence to take place.

"I would argue that maybe the terrestrial planets formed first and then the giant planets just stopped forming when there was no more gas," Cauê Borlina, an assistant professor of planetary science at Purdue University, told Live Science. "After that, it just becomes this chaotic buildup."

Determining a planet's age

Scientists are still debating which theory best explains the solar system's formation. But even the way they think about the age of a planet isn't straightforward.

"There are two different ways of thinking about the age of a planet," Gaia Stucky de Quay, a planetary scientist at MIT, told Live Science. Instead of dating a planet based on its provenance, some scientists focus their attention on its surface.

"The way I think about ages is more the age of the surface, because surfaces can be really old, like a preserved surface, or surfaces can be really young if stuff is still happening" like active plate tectonics, Stucky de Quay said.

One method scientists use to determine a planet's age is to manually count the craters on its surface. From this perspective, Earth could be considered the youngest planet, as its surface changes continuously, with Venus and Mars coming next, she said.

Unfortunately, the limitations of current planetary dating methods mean that scientists can only estimate how old each planet is. And because even a small margin of error can amount to millions of years in the history of the universe, researchers are still working to gather data to piece together a more precise timeline.

"If we ever want to try to get this full picture of how and when planets form, I think samples are a crucial part of that," Borlina said. "And some places are a little bit harder than ours to get samples from, but we have samples sitting on Mars right now just waiting for us to bring them back."

Scientists have discovered that the molecular building blocks needed for life are "readily available" on Saturn's icy moon Enceladus.

At only 314 miles (505 kilometers) wide, Enceladus could fit inside Colorado — and thanks to its liquid water, hydrothermal energy source and chemical tool kit, it has the potential to host extraterrestrial life.

Twenty years ago, NASA's Cassini spacecraft discovered evidence that a vast salty ocean hidden beneath Enceladus' surface was spitting out minuscule "ice grains" through cracks near the moon's south pole. Subsequent studies have spotted five of the six essential elements for life — carbon, hydrogen, nitrogen, oxygen and phosphorus (only missing sulfur) — within these grains.

However, the majority of these past studies looked at the relatively old ice grains that settled in Saturn's E ring — a diffuse ring outside the planet's bright main rings — after being ejected decades or centuries prior. This meant scientists couldn't be sure that the compounds truly came from Enceladus rather than from space weathering in the ring.

Now, astronomers have identified organic molecules, perhaps including nitrogen and oxygen, in fresh ice grains sprayed from Saturn's icy moon. The new research was published Wednesday (Oct. 1) in the journal Nature Astronomy.

Secrets of the ice moon

In 2008, as Cassini shot through a geyser of freshly spewed-up ice grains from Enceladus, it collected data on the splatter that covered the spacecraft's Cosmic Dust Analyzer. These grains hit the spacecraft at 11 miles per second (18 kilometers per second), which was so fast that the water molecules didn't cluster. This meant the team could see "previously hidden signals," study co-author Nozair Khawaja, a planetary scientist at the Free University of Berlin, said in a statement.

The researchers used mass spectrometry to analyze the chemical fingerprint of the molecules in the fresh ice grains. They found chemical compounds that, on Earth, are involved in reactions that lead to the formation of complex molecules required for life, including structures potentially containing nitrogen and oxygen.

"These molecules we found in the freshly ejected material prove that the complex organic molecules Cassini detected in Saturn's E ring are not just a product of long exposure to space, but are readily available in Enceladus's ocean," study co-author Frank Postberg, a professor of planetary science at the Free University of Berlin, said in the statement.

Nozair said there are various ways these molecules could become biologically relevant, "which enhances the likelihood that the moon is habitable." Even so, he said it would still be a huge discovery to not find any life on Enceladus because it would raise "serious questions about why life is not present in such an environment when the right conditions are there."

ESA is planning a future mission to land a spacecraft on the southern pole of Enceladus to collect more samples. The agency is targeting the early 2040s as the earliest possible launch date.

The asteroid belt is found orbiting between Mars and Jupiter and is a vast collection of rocks that is thought to be a planet that never formed. When our Solar System formed 4.6 billion years ago, the material in this region should have coalesced into a planet, however, Jupiter's gravitational influence prevented this from happening, stirring up the region so that collisions became destructive rather than constructive. What remains today contains only about 3% of the Moon's mass scattered across millions of kilometres.

Jupiter's influence didn't stop there. Gravitational resonances, areas in space where the orbital periods of asteroids create regular interactions with Jupiter, Saturn, and even Mars, destabilise asteroid orbits, flinging fragments either toward the inner Solar System, where Earth resides, or outward toward Jupiter's orbit. Asteroid fragments that don't escape are ground down by mutual collisions into meteoritic dust.

A team of astronomers led by Julio Fernández from the Universidad de la República in Uruguay has calculated precisely how fast this depletion of asteroid belt material is progressing. They found that the asteroid belt is currently losing approximately 0.0088% of the portion of the asteroid belt that's still participating in the ongoing collisions. That might sound like a small number but it represents a significant flow of material when considered over the immense timescales of Solar System evolution.

What makes this result particularly interesting is how that lost mass splits up between different fates. About 20% escapes as asteroids and meteoroids that occasionally cross Earth's orbit and sometimes make rather dramatic entrances into our atmosphere as meteors. The remaining 80% is ground down through mutual collisions into meteoritic dust that feeds the faint glow that is the zodiacal dust that is visible in the night sky after sunset or before sunrise. The more familiar asteroids like Ceres, Vesta, and Pallas were excluded from the study since they have survived sufficiently long to no longer be participating in the ongoing depletion of material.

Understanding the asteroid belt's mass loss is important and has a direct implication for Earth's evolution. The large bodies that escape the belt don't simply vanish into space, some eventually find their way to the inner Solar System, where they become potential impactors. The research suggests that if the current mass loss rate is extrapolated backward in time, the asteroid belt could have been about 50% more massive around 3.5 billion years ago, with a mass loss rate about twice as high. This correlates remarkably well with geological evidence from the Moon and Earth showing a declining bombardment rate over the past few billion years.

The asteroid belt, is often considered to be a permanent feature of our Solar System, but this research reveals it as a dynamic structure that's been gradually losing material for billions of years. The glass spherule layers found in Earth's rock strata reveal a more violent past when a more massive asteroid belt sent far more chunks of rock our way. Today, that bombardment has settled into a steady trickle as the belt continues its slow decline. Understanding this process not only helps us piece together the impact history that shaped Earth's surface but it also provides crucial data for modeling the future risk from near Earth objects.

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

The James Webb Space Telescope has discovered strange "dark beads "above a four-armed star pattern in Saturn's atmosphere. The surprising structures are unlike anything scientists have seen before, and they're not sure what they are.

The unusual features were discovered by the James Webb Space Telescope's (JWST's) Near Infrared Spectrograph (NIRSpec) as it peered into the gas giant's atmosphere above the hexagonal storm that swirls at the planet's north pole.

The astronomers expected to see emissions across broad bands of the infrared spectrum in the atmospheric layers above the vortex. Yet what they noticed instead were dark, bead-like features — separated by vast distances yet possibly interconnected — drifting slowly in the charged plasma of the planet's ionosphere, and a lopsided star-shape structure in the stratosphere beneath. They published their findings Aug. 28 in the journal Geophysical Research Letters.

"The results came as a complete surprise," Tom Stallard, a professor of astronomy at Northumbria University in the U.K., said in a statement. "These features were completely unexpected and, at present, are completely unexplained."

Saturn's Hexagon was first discovered in 1980 by NASA's Voyager spacecraft and imaged in fine detail by the Cassini spacecraft, which orbited the planet from 2004 to 2017. It rises as an 18,000-mile-wide (29,000 kilometers) six-sided tower whirling above the planet's surface, making a complete rotation roughly once every 10 hours.

Scientists believe that the hexagon is driven by a jet stream circling the planet's pole, and owes its unique shape to the properties of the gases in Saturn's atmosphere. Yet the exact reasons it has this flow and shape aren't known for certain; and neither is the behavior of the upper atmosphere above it, due to the very weak emissions coming from it.

To investigate, the astronomers focused JWST's NIRSpec instrument on Saturn's ionosphere and stratosphere, located 684 miles (1,100 km) and 373 miles (600 km) above the planet's nominal surface, respectively.

Related: Saturn will be at its biggest and brightest on Sept. 21 — here's how to see it

Over 10 hours, the telescope tracked positively-charged hydrogen molecules (H3+, involved in many reactions in the planet's atmosphere) across Saturn's ionosphere and methane molecules throughout its ionosphere, revealing the strange structures.

"We think that the dark beads may result from complex interactions between Saturn's magnetosphere and its rotating atmosphere, potentially providing new insights into the energy exchange that drives Saturn's aurora," Stallard said.

The asymmetric star pattern, meanwhile, may somehow be tied to the hexagonal storm pattern, he said.

"Tantalisingly, the darkest beads in the ionosphere appear to line up with the strongest star-arm in the stratosphere, but it's not clear at this point whether they are actually linked or whether it's just a coincidence," he added.

To understand what could be causing the features, and their effects on Saturn's atmosphere, the team hopes to conduct followup observations with JWST. Saturn is currently at its equinox, meaning the patterns could change drastically as the sun shifts across the planet's face. On Sept. 21, the ringed planet will also be at its closest point to Earth — the best time to observe Saturn with telescopes and to attempt to parse its many mysteries.

Pluto is a bit of a loner. The dwarf planet is no longer considered a regular planet; it does not orbit on the same plane as the solar system's eight planets; and its orbit is both highly elliptical and extremely tilted.

In fact, its orbit is much more similar to that of its neighbors in the Kuiper Belt, a doughnut-shaped region beyond Neptune's orbit that's also home to other dwarf planets like Makemake and Eris, as well as millions of icy objects. But even compared with the rest of the objects in the Kuiper Belt, Pluto's orbit is peculiar.

So, how did Pluto's orbit end up this way?

First, let's compare Pluto to Earth and other planets in the solar system. The dwarf planet's orbit has an eccentricity — how much it deviates from a perfect circle — of 0.25. For comparison, Earth's orbit has an eccentricity of 0.0167, meaning it's nearly circular. Saturn and Mars have eccentricities of 0.054 and 0.093, respectively.

Pluto's orbit is tilted 17.4 degrees, compared with Earth's 1.5 degrees and Mercury's roughly 2 degrees.

Pluto's unusual eccentricity and tilt is likely due to its interactions with neighboring Neptune and other giant planets, said Renu Malhotra, a planetary scientist at the University of Arizona who has studied Pluto's orbit extensively.

Related: Why aren't all orbits circular?

Scientists believe Neptune's migration due to gravitational interactions with its giant neighbors plays a part in explaining Pluto's orbit. At some point, the planets migrated, and Pluto "was in this kind of orbit because Neptune's orbit had migrated outward … and swept Pluto up into this resonance," or when the gravities of orbiting bodies periodically influence each other as they pass nearby, Malhotra told Live Science.

Say you have a flat surface, Malhotra said. If you randomly toss rocks on it, they'll end up anywhere. But if you have dips in the surface, the rocks will end up in those dips. In the case of the planets, Neptune's migration created a gravitational well for resonant objects like Pluto.

Neptune keeps Pluto in check despite its strange orbit. For 20 years of 248-year orbit, Pluto is inside Neptune's orbit. The two planets are in a 3:2 orbital resonance, which means that Pluto completes two orbits every time Neptune completes three.

"That configuration is very stable and it protects Pluto from getting jostled further," said Will Grundy, an astronomer at the Lowell Observatory in Arizona and co-investigator on NASA's New Horizons mission to Pluto.

There's another odd aspect of Pluto's orbit. When the dwarf planet reaches perihelion — its closest point to the sun — it's always above the plane of the planets. That's "really peculiar," Malhotra said. Generally, planets and other dwarf planets dip above and below the plane over time — something that simulations suggest Pluto has never done. This is caused by a dance between Pluto and the planets Jupiter and Uranus that works to keep Pluto from launching into chaos.

"We used to think it was just the fact of Neptune and Pluto, but it turns out that the other planets are also very important in this other characteristic of Pluto," Malhotra said.

Pluto isn't alone in having a strange orbit, though. For instance, the dwarf planet Eris has an eccentricity of 0.45 and an inclination of about 43 degrees. "It's a much more extreme orbit," Grundy told Live Science.

There's still a lot to learn about how the planets migrated and by how much. And Pluto's cosmic neighborhood, the Kuiper Belt, is certain to offer even more mysteries.

"There's more landscape on objects [100 kilometers, or about 60 miles, and bigger] in the Kuiper Belt than there is in the entire rest of the solar system combined on solid surfaces," Grundy said. "It really is a ripe area for exploration."

Solar system quiz: How well do you know our cosmic neighborhood?

Scientists in Japan now believe that liquid water once flowed through the heart of the near-Earth asteroid Ryugu, after researchers detected something unusual in the samples of the space rock that were returned to our planet five years ago.

The surprising findings also have potential implications for how Earth acquired its own water, the researchers say.

162173 Ryugu is a roughly 3,000-foot-wide (900 meter) asteroid that orbits the sun every 474 days on a trajectory that frequently overlaps with Earth's. It is unlikely to ever hit our planet, but it is still large enough and comes close enough to us to be considered "potentially hazardous" by NASA.

Ryugu was visited by Japan's Hayabusa2 mission between 2018 and 2019, which deployed a probe that landed on the spinning top-shape space rock and collected samples that were later returned to Earth in December 2020.

In a new study, published Sept. 10 in the journal Nature, researchers unearthed chemical irregularities within these samples, which they say can currently be explained only by the historic presence of flowing water within the asteroid.

"We found that Ryugu preserved a pristine record of water activity," study lead author Tsuyoshi Iizuka, a geochemist at the University of Tokyo in Japan, said in a statement. There is also "evidence that fluids moved through its rocks," he added. "It was a genuine surprise!"

Related: Key building block for life discovered on distant asteroid Ryugu — and it could explain how life on Earth began

The new findings emerged after the team analyzed the radioactive isotopes — rare versions of elements with an altered atomic mass — of lutetium (Lu) and hafnium (Hf) within the samples.

Lu-176 naturally decays into Hf-176 via beta decay, in which an element spits out charged subatomic particles, such as electrons or positrons, transforming them into something else. By working out the ratio of Lu-176 to Hf-176 and comparing it to the half life of Lu-176 — the time taken for half a sample of the isotope to naturally decay — the team aimed to work out how old the samples were.

But when they carried out their analysis, the researchers found that there was far too much Hf-176 in the samples. The researchers argue that the only thing that could properly explain this result was that ancient liquid water had washed away a majority of Lu-176 within the samples, which could have started happening shortly after Ryugu was born.

A watery past

"The most likely trigger [for the water] was an impact on a larger asteroid parent of Ryugu, which fractured the rock and melted buried ice, allowing liquid water to percolate through the body," Izuka said.

Recent analysis from the James Webb Space Telescope (JWST) had suggested that Ryugu's parent asteroid may have also spawned the asteroid Bennu, which was visited by NASA's OSIRIS-REx mission that later returned samples of the asteroid to Earth in September 2023. However, similar signs of flowing water have not been seen within Bennu's samples so far, creating uncertainty about the asteroids' respective origins.

Given that Ryugu likely had flowing water, the researchers also believe that its parent asteroid may have contained ice for at least a billion years after the solar system was formed, which is far longer than most asteroids were thought to be able to hold onto their water.

"This changes how we think about the long-term fate of water in asteroids," Izuka said. "The water hung around for a long time and was not exhausted so quickly as thought."

It is widely accepted that a majority of Earth's water likely came from impacts with asteroids, comets or other planetesimals in the early days of the solar system. The new findings hint that asteroids could have played a much larger role in this process than previously thought, potentially delivering up to three times more water to our planet than expected, the researchers claim.

The study team is now planning to analyze veins of phosphate within the samples, which could pin down a more accurate age for the water that flowed through Ryugu, and look more closely at the isotopes from asteroid Bennu to see if it too has signs of flowing water, according to Live Science's sister site Space.com.

Who hasn't looked into the sky and wondered if there's life out there, somewhere, looking back at us? Is it possible there's alien life closer to home — within the bounds of our solar system?

The short answer is yes, there are several places researchers are looking for signs of life within our solar system, and there are some hints that life might be hiding in unexpected places.

Is there life on Mars?

While there don't seem to be any "little green men" inhabiting Mars, it's possible there was microbial life in the past. Mars is currently a frigid desert, but thanks to Mars rovers that have studied the planet's rocks, we know that a long time ago, it had liquid water — an important condition for life.

"The Curiosity rover was built to search for habitable environments, the kind that could have supported microbial life on Mars in the past, if life ever arose on the Red Planet," said Amy Williams, a geology professor at the University of Florida and a member of both NASA's Curiosity and Perseverance science teams. "Curiosity's payload was selected to accomplish this task by looking for the conditions that we know life on Earth requires — liquid water, a source of carbon, and chemical energy to power a metabolism," she told Live Science.

In addition to studying the Martian environment, the Perseverance rover has been collecting promising rock samples to be returned to Earth for advanced analysis. The Mars Sample Return mission is currently under development by NASA and ESA to travel to Mars, collect the sample cores, and bring them back to Earth. (The Donald Trump administration has proposed cutting NASA funding to pay for this mission, however.)

"At least one of the cores collected has qualities that fit the definition of a possible indicator of ancient microbial life," Williams said of a particularly interesting rock sample. "Returning samples to Earth with the Mars Sample Return architecture would enable us to address some of humanity's most profound questions, including whether we are alone in the universe."

Related: How would we give aliens directions to Earth?

Could there be life on Venus?

Even though it's commonly called Earth's "twin," Venus is probably not the first place anyone might look for life in the solar system. Its surface temperature is hot enough to melt lead, and the average surface pressure is more than 90 times that of Earth. It's wrapped in thick, dense clouds that are mostly made from sulfuric acid, a highly corrosive substance that mixes with water to form acid rain on Earth, damaging flora, fauna and soil.

Despite those hostile conditions, extremophile microbial life might be able to survive high in Venus' atmosphere, where the temperatures and pressures aren't so extreme; perhaps life could find ways to protect itself from sulfuric acid's destructive nature. To find out, MIT is putting together the Morning Star Missions, which will travel to Venus' atmosphere with the ultimate goal of collecting a sample of the planet's clouds and returning it to Earth for better analysis.

"Microbial life might exist in Venus's clouds, despite their composition of concentrated sulfuric acid," Sara Seager, a professor at MIT and the director of the Morning Star Missions, told Live Science. "If we find compelling signs of life on Venus, it would upend our understanding of habitability and prove that life can exist in non-water solvents, opening up the range of worlds where life is possible."

When looking for life, scientists often focus on the search for liquid water because it's a requirement for life on Earth. Finding life on Venus would shatter that limitation — meaning alien life could be a lot stranger than we've thought and there could be a lot more places to look for it.

In 2020, a possible detection of phosphine gas in Venus' clouds became the center of a controversy about signs of life on Venus. Phosphine gas was an unexpected find because most known chemical processes that produce it come from living organisms or from extreme pressures on gas giants. However, the signal was small and critics said it might have been noise in the data. The Morning Star Missions to Venus will give us much more information about the planet's chemistry and possibly confirm if there's phosphine floating in the clouds.

Is there life on the moons of Saturn and Jupiter?

Further out in the solar system, there are several moons orbiting Saturn and Jupiter that could potentially host life, particularly Enceladus and Europa.

Saturn's moon Enceladus has a global subsurface ocean hiding underneath a thick icy shell. The moon constantly spits giant plumes of salty water into space that give scientists a rare opportunity to directly sample the interior of a celestial body other than Earth. The Cassini mission performed several flybys of Enceladus from 2005 through 2017, collecting images and even direct samples from the plumes that are still being analyzed. A 2023 paper in Nature announced that scientists had detected phosphates on Enceladus — meaning scientists have now detected all the basic chemical ingredients for life in the moon's ocean.

Several missions to study astrobiology on Enceladus, with the goal of collecting more samples from the plumes, have been in the works by teams at ESA and NASA, although they're still a long way from getting to the launch pad.

Like Enceladus, Jupiter's moon Europa is an icy world with a global subsurface ocean and water plumes erupting from its surface. Jupiter's massive gravitational pull on the moon provides energy and motion that fuels active geologic activity, and is thought to be the main reason the ocean is warm enough to be liquid. Interactions between the salty ocean and the rocky interior could possibly host life similar to the life found around hydrothermal vents on Earth.

ESA's Jupiter Icy Moons Explorer (Juice) launched on April 14, 2023 with an expected arrival at Jupiter in July 2031, where it will study Jupiter and three of its moons: Europa, Callisto and Ganymede. NASA's Europa Clipper mission launched on Oct. 14, 2024 to reach Jupiter in 2030 and conduct flybys of Europa to study if conditions for life are present.

Titan, another of Saturn's moons, is an extremely unique place in the solar system. It has a methane cycle like Earth's water cycle and a thick nitrogen and methane atmosphere. The Cassini mission performed over 50 flybys of Titan from 2004 through 2017 and launched the Huygens probe that landed on the moon's surface in 2005. These two missions collected data that indicated Titan's atmosphere could probably create complex molecules that are building blocks for life. NASA is putting together a car-sized octocopter to fly on Titan and collect samples at different landing sites.

Where else could life be in the solar system?

There are quite a few other places we might find life in the solar system, including dwarf planets like Ceres. Ceres is thought to have a lot of liquid water under an icy and rocky crust, thanks to images taken by NASA's Dawn mission which visited it in 2015.

The more we explore the solar system, the more places we find that have conditions that could support life. If there is life out there, it's likely not advanced enough to reach out to us, so we'll have to be the first to say hello.

Extraterrestrials quiz: Are you an alien expert, or has your brain been abducted?

Early Earth was a barren wasteland incapable of supporting life until a big protoplanet crash carried in the necessary ingredients, a new study suggests.

That collision of the proto-Earth and a Mars-size body — nicknamed Theia — has been theorized for decades, especially in discussions of how our moon may have formed from the resulting pieces of the crash.

Now, in a new study, scientists say Theia also brought some of life's key ingredients to our world, more than 4 billion years ago.

"We conclude that the moon-forming impactor Theia originated further out in the solar system [than Earth] and was volatile-rich," study lead author Pascal Kruttasch told Live Science in an email. Kruttasch was a doctoral student at the University of Bern when he performed the study.

Volatiles are chemical compounds that can easily be vaporized, like hydrogen and carbon, but are also considered the building blocks of life. Closer to the sun, temperatures are too high for these materials to condense, meaning they remained in a gas phase near the early Earth and other rocky planets. Farther out, however, there is an abundance of volatiles for gas giant planets like Jupiter and Saturn — as well as comets and asteroids.

Theia was therefore a big deal for Earth, Kruttasch said: It likely shipped these volatiles, which are "essential ingredients for life."

In the study, the researchers used a chemical model to examine isotopes (element types) from meteorites, as well as rocks on Earth.

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

The team zeroed in on the radioactive decay of an isotope of manganese, which existed in the early solar system and slowly decayed to chromium over several million years This decay timeline enabled the researchers to precisely track the first 15 million years of Earth's formation. (The solar system itself is roughly 4.5 billion years old.)

Figuring out how life got to Earth and remained for billions of years is a complex issue. "Earth is the only planet we know of that has produced life and sustained it for several billion years. It is unclear what processes took place in Earth's history to make this possible," Kruttasch said.

But peering back at the early solar system gave the team some clues. Proto-Earth and growing planets nearby (which today include Mercury, Venus and Mars) changed quickly in their first 3 million years in an exchange of dust and gas through evaporation and condensation.

However, this exchange process practically ceased after 3 million years because the first rocky planets and gas planets had taken up much of the free matter in our solar system. Simply put, planets closer to the sun were more depleted of volatile elements than those that were farther away due to the higher temperatures of the inner planets closer to the sun.

That's why Earth's volatiles must have come from a large source like Theia, which is estimated to have collided with our planet roughly 4.5 billion years ago. (In line with other studies, the new work assumes Theia is a type of chondrite, which is a stony material rich in carbon and organic compounds that tends to form far out from the sun.)

The larger implication of these findings is that life may be difficult to conjure on exoplanets that are similar to Earth, given that most volatiles may have formed in a different region of the solar system. "This [study] makes it clear that life-friendliness in the universe is anything but a matter of course," study co-author Klaus Mezger, a professor emeritus of geochemistry at the University of Bern, said in a statement.

The researchers published their findings Aug. 1 in the journal Science Advances. However, this wasn't the only recent study to discuss Theia and its impact on Earth's life.

Unrelated research slated to be published in the Nov. 15 issue of the journal Icarus suggests Theia delivered a lot of water to our planet — and is still visible in the mantle of our planet.

This mantle water is a puzzle to geologists, because "water is less dense than the materials typically found in the Earth's mantle, and it was supposed to have come to the crust or oceans," study co-author Pedro Machado, an astrophysicist at Portugal's Institute of Astrophysics and Space Sciences, said in a translated statement.

The simulation-based study suggested that Theia delivered much of the water in the mantle to the early Earth, "and there hasn't been time for this water to reach the surface," Machado added.

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."

The James Webb Space Telescope has spotted a never-before-seen moon orbiting Uranus, bringing the planet's count of natural satellites to 29.

The moon, for now dubbed S/2025 U1, is just 6 miles (10 kilometers) in diameter, which is why it was invisible to other telescopes and the Voyager 2 spacecraft when it made its 1986 flyby of the icy planet.

Now, the James Webb Space Telescope's (JWST) Near-Infrared Camera (NIRCam) has detected glints of sunlight in a series of 10 40-minute long-exposure images of Uranus, which revealed the elusive moon's presence. The discovery hints that much more remains hidden around Uranus, the astronomers who found the moon say.

"No other planet has as many small inner moons as Uranus, and their complex inter-relationships with the rings hint at a chaotic history that blurs the boundary between a ring system and a system of moons," Matthew Tiscareno, a senior research scientist at the SETI Institute in Mountain View, California, and a member of the research team, said in a statement. "Moreover, the new moon is smaller and much fainter than the smallest of the previously known inner moons, making it likely that even more complexity remains to be discovered."

First spotted in 1781 by the German-British astronomer Frederick William Herschel, Uranus is the seventh planet from our sun and orbits it at a distance of 1.8 billion miles (2.9 billion km), nearly 20 times farther than Earth, according to NASA.

This extreme distance means that much of what we know about the far-flung, icy and lopsided planet comes from data gathered by NASA's Voyager 2 spacecraft, which zipped past the ice giant 40 years ago — yet even this information has been revised.

Related: Surprised scientists discover the 'dark sides' of Uranus' moons are the wrong way around

The newfound moon, the 14th member of a system of small moons inside the orbits of the largest moons Miranda, Ariel, Umbriel, Titania and Oberon, is 35,000 miles (56,000 km) from Uranus' center. It has a nearly circular orbit, meaning it may not have moved far from where it formed. Its location within Uranus' dark inner rings (the planet has 13, divided into an inner system and an outer pair) likely explains why it went undetected for so long.

An official name for the newly discovered moon is awaiting approval by the International Astronomical Union (IAU), but it will most likely be named for a character from the works of Shakespeare or Alexander Pope, after which the planet's other moons are named.

The JWST has made a number of astounding observations into the furthest reaches of our universe. But scientists say this discovery, made as part of the space telescope's General Observer program, highlights the JWST ability to discover things at the outer limits of our own solar system.

"Looking forward, the discovery of this moon underscores how modern astronomy continues to build upon the legacy of missions like Voyager 2, which flew past Uranus on Jan. 24, 1986, and gave humanity its first close-up look at this mysterious world," Maryame El Moutamid, a lead scientist at Southwest Research Institute's Solar System Science and Exploration Division in Boulder, Colorado, said in the statement. "Now, nearly four decades later, the James Webb Space Telescope is pushing that frontier even farther."

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.

Four of the solar system's terrestrial planets, including Earth and a long-lost world, likely started life waltzing around the sun to a fixed rhythm, according to a new study. The findings also suggest that those planets formed earlier than previously thought.

Astronomers have been increasingly interested in how planetary systems change their internal architecture on cosmic timescales, motivated by several recent exoplanet family discoveries, like the seven-planet cohort orbiting the tiny star TRAPPIST-1.

Past research has found that one early stage in a planetary family's metamorphosis involves pairs, triplets or entire systems moving in a rhythmic beat — called resonance — around their parent star. Planets in resonance have orbital periods that form a whole-number ratio. In the TRAPPIST-1 system, for instance, the innermost planet, TRAPPIST-1 b, completes eight orbits for five of its nearest neighbor's.

Resonance arises among planets born within a protoplanetary disk — the disk of debris surrounding an infant star — that still contains gas. Such planets plow through the gas, exchanging their rotational motion with it, which often causes them to move toward the star. Many of these planets may come close enough to each other for their orbital periods to "resonate," or become whole-number multiples.

Today, the solar system's planets aren't in resonance (although Venus and Mars come close, with an orbital-period ratio of 3.05:1). But in 2005, astronomers showed that Jupiter and Saturn waltzed in a resonant beat soon after their birth. This dance halted abruptly 4.4 billion years ago, however, when the protoplanetary gas disk started evaporating, pushing Saturn, Uranus and Neptune outward in an event called the giant planetary instability.

Related: What's the maximum number of planets that could orbit the sun?

Until now, though, nobody had examined whether the terrestrial planets have ever been in resonance, Chris Ormel, an associate professor at Tsinghua University in China and co-author of the new study, told Live Science by email. This was because "an alternative theory — that the planets formed by a series of giant impacts — was thought to be adequate" to explain how they currently behave, he said.

But research from 2013 analyzing Martian isotopes suggested that terrestrial planets could have formed when the protoplanetary disk was still rich in gas, about 10 million years after the solar system's birth. This meant the terrestrial planets may have once been in resonance.

To examine the hypothesis, the new study's authors created computer models of the infant solar system. Each model included two giant planets — Jupiter and Saturn — along with four rocky worlds: Mars, Theia (a hypothetical Mars-size object whose collision with early Earth formed our moon), early Earth (prior to Theia’s collision) and Venus. Mercury is widely believed to have been created by giant impacts, so the researchers excluded it from the simulations.

In all of the models, the team placed Saturn closer to Jupiter than it is today and had the rocky worlds grow by accumulating either pebbles or larger, trillion-ton rock blocks. In most simulations, Venus, Earth, Theia and Mars formed a 2:3:4:6 resonant chain within a million years of simulated time.

The researchers then performed 13,200 simulations of the planets' potential movements over a 100-million-year interval, considering the gravitational tugs each planet exerted on the others. At the 10 million-year mark, however, the researchers made Saturn move outward "to simulate the giant planet instability," Shuo Huang, a doctoral student at Tsinghua University and the study's first author, told Live Science by email.

The researchers found that, based on the selected parameters, up to half of the simulations re-created the terrestrial planets' current configuration. This included aspects like the occurrence of a single Theia-Earth collision and the 3.05:1 orbital-period ratio of Venus and Mars — a relic of their past resonance.

Additionally, the findings suggest the planets formed in the gas-filled protoplanetary disk, within the first 10 million years of the solar system's creation, which is at least 20 million years older than current models predict.

One planet that could confirm how old the rocky inner worlds are is Venus. Because it (unlike Earth and Mars) hasn't suffered any giant impacts, the authors think its mantle will reflect its ancient origin. And future missions could collect such mantle samples, Huang said.

The findings also indicate that outer giant planets can destabilize their inner companions tremendously. The authors said this may explain why resonant systems like TRAPPIST-1 don't have giant outer planets.

The new study was published July 18 in The Astrophysical Journal.

Solar system quiz: How well do you know our cosmic neighborhood?

Is there a massive undiscovered planet on the outer reaches of the solar system? The idea has been around since before the discovery of Pluto in the 1930s. Labelled as Planet X, prominent astronomers had put it forward as an explanation for Uranus's orbit, which drifts from the path of orbital motion that physics would expect it to follow. The gravitational pull of an undiscovered planet, several times larger than Earth, was seen as a possible reason for the discrepancy.

That mystery was ultimately explained by a recalculation of Neptune's mass in the 1990s, but then a new theory of a potential Planet Nine was put forward in 2016 by astronomers Konstantin Batygin and Mike Brown at Caltech (the California Institute of Technology).

Their theory relates to the Kuiper Belt, a giant belt of dwarf planets, asteroids and other matter that lies beyond Neptune (and includes Pluto). Many Kuiper Belt objects — also referred to as trans-Neptunian objects — have been discovered orbiting the Sun, but like Uranus they don't do so in a continuous expected direction. Batygin and Brown argued that something with a large gravitational pull must be affecting their orbit, and proposed Planet Nine as a potential explanation.

This would be comparable to what happens with our own Moon. It orbits the Sun every 365.25 days, in line with what you would expect in view of their distance apart. However, the Earth's gravitational pull is such that the Moon also orbits the planet every 27 days. From the point of view of an outside observer, the Moon moves in a spiraling motion as a result. Similarly, many objects in the Kuiper Belt show signs of their orbits being affected by more than just the Sun's gravity.

While astronomers and space scientists were initially skeptical about the Planet Nine theory, there has been mounting evidence thanks to increasingly powerful observations that the orbits of trans-Neptunian objects are indeed erratic. As Brown said in 2024:

"I think it is very unlikely that P9 does not exist. There are currently no other explanations for the effects that we see, nor for the myriad other P9-induced effects we see on the Solar System."

Related: Astronomers discover new dwarf planet 'Ammonite' — and it could upend the existence of Planet Nine

In 2018, for example, it was announced that there was a new candidate for a dwarf planet orbiting the Sun, known as 2017 OF201. This object measures around 700km across (Earth is roughly 18x bigger) and has a highly elliptical orbit. This lack of a roughly circular orbit around the Sun suggested either an impact early in its lifetime that put it on this path, or gravitational influence from Planet Nine.

Problems with the theory

On the other hand, if Planet Nine exists, why hasn't anyone found it yet? Some astronomers question whether there's enough orbital data from Kuiper objects to justify any conclusions about its existence, while alternative explanations get put forward for their motion, such as the effect of a ring of debris or the more fantastical idea of a small black hole.

The biggest issue, however, is that the outer Solar System just hasn't been observed for long enough. For example, object 2017 OF201 has an orbital period of about 24,000 years. While an object's orbital path around the Sun can be found in a short number of years, any gravitational effects probably need four to five orbits to notice any subtle changes.

New discoveries of objects in the Kuiper Belt have also presented challenges for the Planet Nine theory. The latest is known as 2023 KQ14, an object discovered by the Subaru telescope in Hawaii.

It is known as a "sednoid", meaning it spends most of its time far away from the Sun, though within the vast area in which the Sun has a gravitational pull (this area lies some 5,000AU or astronomical units away, where 1AU is the distance from the Earth to the Sun). The object's classification as a sednoid also means the gravitational influence of Neptune has little to no effect on it.

2023 KQ14's closest approach to the Sun is around 71AU away, while its furthest point is about 433AU. By comparison, Neptune is about 30AU away from the Sun. This new object is another with a very elliptical orbit, but it is stabler than 2017 OF201, which suggests that no large planet, including a hypothetical Planet Nine, is significantly affecting its path. If Planet Nine exists, it would therefore perhaps have to be farther than 500AU away from the Sun.

To make matters worse for the Planet Nine theory, this is the fourth sednoid to be discovered. The other three also exhibit stable orbits, similarly suggesting that any Planet Nine would have to be very far away indeed.

Nonetheless, the possibility remains there could still be a massive planet affecting the orbits of bodies within the Kuiper Belt. But astronomers' ability to find any such planet remains somewhat limited by the restrictions of even unmanned space travel. It would take 118 years for a spacecraft to travel far enough away to find it, based on estimates from the speed of NASA's New Horizons explorer.

This means we'll have to continue to rely on ground- and space-based telescopes to detect anything. New asteroids and distant objects are being discovered all the time as our observing capabilities become more detailed, which should gradually shed more light on what might be out there. So watch this (very big) space, and let's see what emerges in the coming years.

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

A tiny meteorite is rewriting what scientists thought they knew about the origins of our solar system.

New evidence found in shavings from a meteorite known as Northwest Africa 12264 — a 50-gram (1.8 ounces) piece of space rock that is believed to have formed in the outer solar system — suggests that rocky planets like Earth and distant icy bodies may have formed at the same time. This challenges the long-standing belief that planets closer to the sun formed before those in the outer solar system, the ones that lie beyond the asteroid belt between Mars and Jupiter.

Planets form within the rotating disks of gas and dust that surround young stars, where particles collide and stick together through a process known as accretion. As developing rocky planets heat up, they begin to differentiate, forming separate internal layers known as the core, mantle and crust.

Scientists have thought that our solar system's inner rocky planets — Mercury, Venus, Earth and Mars —formed first (around 4.566 billion years ago), while gas giants and icy bodies in the outer solar system came together slightly later (4.563 billion years ago), due to the colder temperatures at a greater distance from the sun. Rocky planets farther out were also thought to form more slowly because their higher water and ice content would have delayed internal heating and core development.

Analyzing the composition of the meteorite (which was purchased from a dealer in Morocco in 2018) revealed a ratio of chromium and oxygen that indicates it came from the outer part of the solar system. Using precise isotopic dating methods, the researchers found that the rock formed 4.564 billion years ago — just two to three million years after the solar system’s earliest solid materials.

Related: How many meteorites hit Earth every year?

Until now, such early formation was thought to be limited to bodies from the inner solar system, according to a statement announcing the new study.

Evidence that rocky planets beyond Jupiter formed as rapidly, and at the same time, as the inner planets could transform our understanding of how planets take shape — not only in our solar system, but in planetary systems throughout the universe, the researchers said.

Their findings were published on July 4 in the journal Communications Earth & Environment.

This article was originally published on Space.com.

Astronomers have discovered a possible new dwarf planet orbiting far beyond Pluto. First detected in March 2023 by Japan's Subaru Telescope in Hawaii, this object has been dubbed 2023 KQ14 and nicknamed Ammonite. Ammonite's appearance also puts a kink in what's known as the Planet Nine hypothesis, which suggests there may be an undiscovered ninth planet in our solar system.

Led by researchers in Japan, the team announced Ammonite's discovery in a paper published July 14 in the journal Nature Astronomy. The body gets its moniker from the fossil of a long-extinct cephalopod because it was identified as part of the survey project Formation of the Outer Solar System: An Icy Legacy, or FOSSIL.

Ammonite is classified as a sednoid, which is an object beyond Neptune — our solar system's outermost confirmed planet — with a peculiar orbit. It's now the fourth sednoid discovered. The term "sednoid" comes from the dwarf planet Sedna, which exists at our solar system's edge and was discovered in 2004.

When describing the orbits of celestial bodies, astronomers use astronomical units (AU). The distance between Earth and the sun is approximately 1 AU. Following an elliptical path, Sedna is about 76 AU from the sun at its nearest point (perihelion) and 900 AU at its farthest (aphelion). Ammonite, meanwhile, is between 66 and 252 AU from the sun at the closest and farthest points in its orbit.

The discovery of 2023 KQ14 detracts from the possibility that there could be a ninth planet for our solar system, according to the study authors. First proposed in 2016, the Planet Nine hypothesis suggests there may be a Neptune-size planet orbiting the sun about 20 to 30 times farther from the sun than Neptune is.

This planet would explain the eccentric orbits of smaller bodies in the Kuiper Belt, which is the vast expanse of icy rocks that encompasses the outer solar system. It's believed that the gravity of a much more massive body, like a planet, may be shepherding these smaller objects. However, the relationship between the newest sednoid's orbit and that of the other three known sednoids calls this hypothesis into question.

"The planet 9 hypothesis is based on the fact that the known Sednoids have their orbit cluster on one side of the solar system," study co-author Shiang-Yu Wang, a research fellow at the Institute of Astronomy and Astrophysics in Taiwan, told Live Science in an email.

Related: What are dwarf planets — and how many are there?

Ammonite is unique among these sednoids because its orbit is on the opposite side — its furthest point from the sun is in the opposite direction from the other sednoids' furthest points. The fact that there is now a known object orbiting on this path decreases the possibility that a large planet could be out there, too.

"The fact that 2023 KQ14's current orbit does not align with those of the other three sednoids lowers the likelihood of the Planet Nine hypothesis," study co-author Yukun Huang, a project research fellow at the National Astronomical Observatory of Japan's Center for Computational Astrophysics, said in a press release. "It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today."

Other astronomers also believe Ammonite throws a wrench in this hypothesis. "The trouble is the evidence from the alignment has never been scientifically convincing and hasn't really grown stronger, even over the last 10 years or so," David Jewitt, a professor of astronomy at the University of California, Los Angeles who was not involved in Ammonite's discovery, told Live Science.

"Ammonite does not align with these six other objects, so weakens the case for Planet Nine, or means it must be very remote and correspondingly difficult to detect," Christopher Impey, an astronomy professor at the University of Arizona who was not involved in the sednoid's discovery, told Live Science.

But Impey is confident that, if there really is a Planet Nine, the newly activated Vera C. Rubin Observatory in Chile will soon be able to confirm it. "If Planet Nine exists, it will almost certainly be found in that survey data within a few years," he said.

Scientists have found that Uranus is emitting its own internal heat — even more than it receives from sunlight — and this discovery contradicts observations of the distant gas giant made by NASA's Voyager 2 probe nearly four decades ago.

Scientists led by Xinyue Yang of the University of Houston analyzed decades of readings from spacecraft and computer models to find that Uranus emits 12.5% more internal heat than the amount of heat it receives from the sun. However, that amount is still far less than the internal heat of other outer solar system planets like Jupiter, Saturn and Neptune, which emit 100% more heat than they get from the sun.

The researchers behind this new study say Uranus' internal heat could help reveal the origins of the curious, tilted world. "This means it's still slowly losing leftover heat from its early history, a key piece of the puzzle that helps us understand its origins and how it has changed over time," Wang said in a statement.

In 1986, the iconic Voyager 2 probe flew by Uranus while headed out of the solar system and into interstellar space. A good deal of what scientists understand about the seventh planet from the sun comes from that flyby, that found that Uranus does not reveal significant internal heat.

But it turns out that we may have caught Uranus at a weird time, and some of the readings Voyager 2 collected could have been skewed by a surge in solar weather that occurred during its flyby of the planet.

By reviewing a large set of archival data and combining that with computer models, researchers now believe the internal heat emitted by Uranus could imply a completely different internal structure or evolutionary history for the planet we thought we knew. Its believed that Uranus formed around 4.5 billion years ago along with the rest of the solar system, and NASA believes it formed closer to the sun before moving to the outer solar system around 0.5 billion years later. That story, however, is now called into question by these new findings.

"From a scientific perspective, this study helps us better understand Uranus and other giant planets," Wang said in the statement. The researchers also believe this new understanding of Uranus' internal processes could help NASA and other agencies plan for missions to the distant planet.

In 2022, the National Academy of Sciences flagged a mission concept known notionally as Uranus Orbiter and Probe (UOP) as one of the highest-priority planetary science missions for the next decade. But even then, before massive budget uncertainty hit NASA and the science community in the wake of President Donald Trump's overhaul of U.S. government spending, scientists knew such an ambitious and expensive mission would be difficult to put into motion.

"There are many hurdles to come — political, financial, technical — so we're under no illusion," Leigh Fletcher, a planetary scientist at the University of Leicester in the U.K. who participated in the decadal survey process, told Space.com in 2022 when the report was published. "We have about a decade to go from a paper mission to hardware in a launch fairing. There's no time to lose."

Whether or not new research into Uranus helps boost support for such a mission, scientists are already hailing these new results as groundbreaking on their own. Study co-author Liming Li said the study of Uranus' internal heat not only helps us understand the distant, icy world better, but could also help inform studies of similar processes here on Earth, including our own changing climate.

"By uncovering how Uranus stores and loses heat, we gain valuable insights into the fundamental processes that shape planetary atmospheres, weather systems and climate systems," Li said in the statement. "These findings help broaden our perspective on Earth's atmospheric system and the challenges of climate change."

A study on Uranus' internal heat was published in the journal Geophysical Research Letters.

This article was originally published on Space.com.

Our solar system has been around for 4.6 billion years. While that sounds like a long time, it's just a blip in the 13.8 billion-year story of the universe. And one day, the solar system will cease to exist.

But when will the solar system end? And how will it die out?

The answers to those questions depend on how we define the death of the solar system.

The solar system consists of eight planets, several dwarf planets, hundreds of moons, and billions of asteroids, comets and meteoroids. The exact boundaries of the solar system are subject to debate, but there are three main candidates: the Kuiper Belt, a region of icy objects beyond Neptune; the heliopause, where the sun's magnetic field ends; and the Oort cloud, a theoretical icy cloud lying beyond both the Kuiper Belt and the heliosphere. And, of course, at the center of it all, the sun is keeping it all together with its immense gravity.

Like all stars, the sun will eventually die. Right now, it creates heat and light by transforming hydrogen into helium in its core through a process called nuclear fusion. The sun will continue to burn hydrogen for approximately another 5 billion years, said Fred Adams, a theoretical astrophysicist at the University of Michigan. But once that hydrogen fuel runs out, the sun will become more and more unstable. Its core will collapse, its surface will expand, and it will transform into a cool, bloated red giant that will engulf Mercury and then Venus.

While our planet might be at the border of the red giant's surface, Adams said, chances are, it will get sucked into the red giant, too. By this point, though, humans will have been long gone. Mars will likely survive the red giant, and the outer planets are all safely outside of the red giant's reach. The Oort cloud will also be destabilized, Stern said, and the heliosphere will shrink down.

Related: When will the universe die?

About a billion years later, the sun will shrink to the size of Earth and transform into a white dwarf — a dim, extremely dense core of its former self. The solar system will become a freezing, desolate place.

"From a habitability standpoint, that's kind of the end of the solar system," Alan Stern, a planetary scientist and principal investigator of NASA's New Horizons mission, told Live Science.

Although the sun's death marks the end of the solar system as we know it, it doesn't necessarily mean its total demise. "A strict, nerdy answer is that the solar system will never end due to the sun's evolution" or the death of the sun, Stern said. Even when the sun is a burnt out cinder, he said, many objects — including giant planets like Jupiter — will continue to orbit it.

Even further into the future, Adams said, the likelihood of rare events increases. Without the sun's gravitational force, the solar system will become increasingly chaotic as the gravitational balance of the solar system shifts. The risk of collisions, passing stars or supernovas coming too close to the solar system and then tearing apart its celestial bodies and space rocks will also be magnified.

"We're not just waiting until the universe is twice as old. We're waiting till it's a billion times older, a trillion times older, and a quadrillion times older," he explained. "If you wait, those enormous time scales and rare events start to add up. It's like, it's rare for you to win the lottery, but if you play a billion times, your chances will go up."

Even if the solar system is spared a catastrophic collision, it won't last forever. Some scientists also think the protons that make up our universe will decay. The phenomenon has never been observed, but theoretical experiments have placed the proton's lifetime past 10³⁴ years, and that number might be pushed back even further as experiments into their longevity keep running.

Solar system quiz: How well do you know our cosmic neighborhood?

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.

Over the next few months, there will be several chances to see a giant "hole" shoot across the surface of Saturn, as the shadow of its largest moon passes across the ringed planet's Earth-facing surface. The rare spectacle will not be visible again until 2040 — and we'll tell you how to see it from your backyard.

Every 15 years, Saturn and Earth become perfectly aligned so that the gas giant's rings face our planet head-on. In March, this alignment was so perfect that the planet's super-thin rings completely disappeared from view, Live Science's sister site Space.com previously reported. In 2032, the opposite will occur, and we will be able to see the entirety of the dusty disks in a perfect circle around the fifth planet from the sun.

Saturn's current orientation also means that the planet's largest moon, Titan, circles it in a way that causes its large shadow to repeatedly transit the planet's surface, similar to how the moon's shadow races across Earth during a lunar eclipse. The same phenomenon also happens to some of Saturn's other major moons, including Mimas and Rhea. However, their respective shadows are smaller and lighter than Titan's, making it harder to see them.

Titan orbits Saturn roughly every 16 days, meaning that there will be a total of 10 transits visible while Earth is still aligned with the ringed gas giant. Three of these transits have already happened, most recently on June 16. But there are still seven more occasions when the spectacle could be visible between now and mid-autumn, depending on your location and weather conditions at the time.

The remaining transits will occur on July 2, July 18, Aug. 3, Aug. 19, Sept. 4, Sept. 20 and Oct. 6, according to Sky & Telescope. For exact times, check the table below.

Related: Saturn gains 128 new moons, giving it more than the rest of the solar system combined

Titan will also be visible during these transits, although its position relative to the shadow changes with each viewing, as Saturn continues to circle the sun. But it will be slightly smaller than the shadow it casts.

To see the spectacular transits for yourself, you will need a good telescope with at least 200x magnification. From North America, most of the transits will start and end before sunrise. To find where Saturn will be in the night sky, you can use websites such as TheSkyLive.com.

However, we recommend that you don't leave it to the last minute, because adverse weather conditions could completely obscure your view. As you can see from the table below, the length of transits will also decrease each time, which means you will have to be more precise with your timings later in the year; On Oct. 6, the shadow will only be momentarily visible when Titan is exactly at mid-transit.

But even if you miss the impressive shadow over the next few months, you will still be able to see Titan pass in front of Saturn every 16 days, up until January 2026, when it will stop transiting the planet until 2040.

If you are lucky enough to see the stunning celestial spectacle, be sure to keep in mind that Titan is the second-largest moon in the solar system, behind Jupiter's behemoth satellite Ganymede. At more than 3,200 miles (5,150 kilometers) across, it is also slightly bigger than the planet Mercury and 50% wider than Earth's moon.

It is also the only one of the solar system's moons, other than Earth's, that has been visited by a human-made spacecraft. The European Space Agency's Huygens probe landed on the Saturnian satellite in 2005 — and it is still there today.

Solar system quiz: How well do you know our cosmic neighborhood?

The James Webb Space Telescope (JWST) has captured its first direct image of a planet in a remote solar system, and it's lighter than any seen before.

The planet, named TWA 7b, is a gas giant with a size comparable to Saturn's. Orbiting a star just over 6 million years old, the planet is still glowing hot from its formation.

The planet is the first observation of hypothesized yet previously unseen "shepherd" planets, which clear gaps of material found inside planetary rings. The researchers behind the discovery published their findings June 25 in the journal Nature.

"It tells us that indeed, planets can form gaps in disks (which was theorised, but not observed) and trojan-like structures can indeed be present in exoplanetary systems," lead study author Anne-Marie Lagrange, an astronomer and research director at the French National Center for Scientific Research (CNRS) in Paris, told Live Science.

"It is the first time that such a light planet is imaged, ten times lighter than the lightest [previously known] planet," she said. "This is thanks to the extreme sensitivity of JWST in the thermal domain."

Astronomers study exoplanets because they help them to understand how planetary systems, such as our own, form. Yet while thousands have been seen indirectly — through the dimming of host stars as they pass in front of them or the wobble the planets' gravitational tugs give them — the light bouncing off exoplanets is usually drowned out by the light from the star, making them effectively invisible.

Related: 'Eyeball' planet spied by James Webb telescope might be habitable

To peer through this glare, JWST uses a coronagraph attached to its Mid-Infrared Instrument (MIRI); this device blocks out a star's light and makes it easier to spot objects orbiting around it. To further boost the effectiveness of this search, astronomers select young stars whose planetary disks are pole-on to the telescope, enabling them to “look down” over star systems whose satellites are still glowing hot from their formation.

The system containing TWA 7b, called TWA 7, is 110 light-years from Earth and contains three concentric rings of rocky debris and dust, one of which was narrow and flanked by two empty bands of space. Within the heart of this narrow ring, the scientists found a hole containing a source of infrared-radiation.

Follow-up simulations suggested that this radiation source is a planet roughly 30% the size of Jupiter that's orbiting its star at 52 times the distance that Earth orbits the sun. Its presence in a gap inside the planetary ring is also intriguing; while observations of holes in the discs surrounding stars have been made before in other systems, this is the first clear detection of the shepherd planets believed to create them.

To further investigate the new system and others like it, Lagrange said that she and her colleagues will obtain "more data to study TWA7 b atmosphere, to search for other light, cold young planets in imaging" and "to search for cold old massive planets."

What's better than the sight of clouds on Mars? The view of a volcano rising above them! This stunning panorama shows the ancient Martian volcano Arsia Mons peeking through clouds on the Red Planet. The image was captured by NASA's Mars Odyssey orbiter just before the first rays of sunlight illuminated the planet on May 2.

The Mars Odyssey mission was launched in 2001 to map the chemical elements and minerals on the Martian surface. Although it completed its primary mission in 2004, it has continued mapping the Red Planet's surface rocks, studying its clouds and fog, and monitoring its seasons ever since.

In 2023, Odyssey started taking high-altitude images of the edge of Mars' horizon, or "limb," like the one shown here. Because the orbiter's cameras are built to capture and study the Martian surface, it can be tricky to snap images of the planet's clouds.

To do so, Odyssey rotates 90 degrees in its orbit so the camera can capture the cloudy layers and see the dust and water ice inside them. Scientists study the Martian atmosphere to learn about the variations in seasons that hint at how the atmosphere evolves. This knowledge can help them anticipate intense winds and dust storms, which are important factors for planning the entry, descent and landing of future missions.

Related: 28 gorgeous nebula photos that capture the beauty of the universe

In the new panorama photo, the Martian atmosphere appears as a greenish haze as Arsia Mons, one of the largest volcanoes on Mars, rises out. Appearing as a dark blob, it peeks above the morning cloud tops, marking the first time a volcano has been imaged on the Red Planet's horizon. Although Arsia Mons is not the tallest volcano on Mars (that honor goes to Olympus Mons), it stands 12 miles (20 km) high, which is more than twice the height of Earth’s highest mountain, Mount Everest.

Arsia Mons is a shield volcano, named for its resemblance to a shield, located in the Tharsis Montes volcanic region on Mars, which includes two other shield volcanoes: Pavonis Mons and Ascraeus Mons. This volcanic region is frequently surrounded by clouds of water ice, with Arsia Mons being the cloudiest of the three, particularly in the early morning. By contrast, carbon dioxide clouds are more prevalent on Mars.

The thick canopy of early-morning clouds is particularly prominent when Mars is at its farthest point from the sun, known as aphelion. During this time, the clouds that form around the equator are known as the aphelion cloud belt. These early-morning clouds are seen parading around Arsia Mons in the image.

The new panorama that marks the fourth "limb" observation was captured by the Thermal Emission Imaging System (THEMIS) camera on the 24-year-old orbiter. THEMIS, which takes pictures in visible and infrared light, helps scientists map the subsurface areas that contain water ice. Identifying such areas could be helpful for deciding the landing sites for the first astronauts on Mars.

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

Astronomers have discovered that the "dark sides" of Uranus' largest moons aren't where they originally thought — and in some cases are on the complete opposite sides of the icy satellites than expected.

Uranus has 28 confirmed moons, including five major moons. The closest of these large satellites is Miranda, followed by Ariel, Umbriel, Titania and Oberon — all named after characters from plays written by William Shakespeare. These icy bodies, which range from 293 to 980 miles (472 to 1,578 kilometers) wide, are all "tidally locked" to Uranus, meaning that the same half of the moon always faces the planet, similar to how Earth's moon orbits our planet.

Because of this tidal locking, the major moons have a "leading side," the hemisphere facing forward in their respective orbits, and a "trailing side," which is always looking back in the satellites' wake. Scientists had assumed that the leading sides of each moon would be brighter when viewed in invisible wavelengths of electromagnetic light, such as ultraviolet and infrared. This is because electrons from the planet's magnetic field, or magnetosphere, should be captured by the moons and naturally accumulate on their trailing sides, scattering radiation and making them appear "darker," similar to some other moons in the solar system.

But in a new study, researchers turned the ultraviolet instruments of the Hubble Space Telescope toward Ariel, Umbriel, Titania and Oberon to measure their brightness. Surprisingly, none of the moons' leading sides were brighter than their respective trailing sides, and on Titania and Oberon, the trailing side was brighter than the leading side, flipping the current theory on its head.

The team shared their findings on Tuesday (June 10) at the 246th American Astronomical Society meeting in Anchorage, Alaska. The results have not yet been published in a peer-reviewed journal.

Related: Scientists finally know how long a day on Uranus is

While the new findings were a shock, they can be partially attributed to confusion around the magnetic properties of the solar system's seventh planet. "Uranus is weird, so it's always been uncertain how much the magnetic field actually interacts with its satellites," Richard Cartwright, a planetary scientist at the John Hopkins University in Maryland and principal investigator of the study team, said in a statement.

Most of this confusion comes from Uranus' unusual tilt. The planet's axis is tilted 98 degrees relative to its orbit around the sun — giving it the appearance of a rolling ball, rather than a spinning top — but its satellites still orbit around its equator, meaning they pass through the magnetosphere at a 59-degree angle. Recent findings also hint that scientists' current assumptions about the magnetosphere's size and strength may be wrong, due to magnetic anomalies that occurred 40 years ago when the Voyager 2 probe took the first up-close measurements of the planet.

The new study does not really help us learn anything about Uranus' magnetosphere because the lack of electrons could be explained by either a weaker magnetic shield or a much stronger and more chaotic one, the researchers said.

However, the unexpected brightness of Titania's and Oberon's trailing sides hint at another unknown phenomenon, which researchers have dubbed "dust shielding." The idea is that little bits of dust around Uranus, which have accumulated over millions of years of meteor strikes on the Uranian moons, are hitting the moons' leading sides "like bugs hitting the windshield of your car as you drive down a highway," researchers said.

"This is some of the first evidence we're seeing of a similar material exchange among the Uranian satellites," added co-investigator Bryan Holler, a support scientist at the Space Telescope Science Institute in Maryland that oversees Hubble's science operations. However, similar exchanges have been observed in the systems of Jupiter and Saturn, he added.

This is not the only surprising discovery made about Ariel, Umbriel, Titania and Oberon. Recent findings have also hinted that all four of these major moons could support or have previously supported subterranean oceans, similar to those believed to exist on Europa, Ganymede and Enceladus.

The researchers hope that the mysteries surrounding Uranus' moons could soon be unraveled by the James Webb Space Telescope, which has already helped uncover many of the planet's secrets using its state-of-the-art infrared instruments.

My telescope, set up for astrophotography in my light-polluted San Diego backyard, was pointed at a galaxy unfathomably far from Earth. My wife, Cristina, walked up just as the first space photo streamed to my tablet. It sparkled on the screen in front of us.

"That's the Pinwheel galaxy," I said. The name is derived from its shape – albeit this pinwheel contains about a trillion stars.

The light from the Pinwheel traveled for 25 million years across the universe – about 150 quintillion miles – to get to my telescope.

My wife wondered: "Doesn't light get tired during such a long journey?"

Her curiosity triggered a thought-provoking conversation about light. Ultimately, why doesn't light wear out and lose energy over time?

Let's talk about light

I am an astrophysicist, and one of the first things I learned in my studies is how light often behaves in ways that defy our intuitions.

Light is electromagnetic radiation: basically, an electric wave and a magnetic wave coupled together and traveling through space-time. It has no mass. That point is critical because the mass of an object, whether a speck of dust or a spaceship, limits the top speed it can travel through space.

But because light is massless, it's able to reach the maximum speed limit in a vacuum – about 186,000 miles (300,000 kilometers) per second, or almost 6 trillion miles per year (9.6 trillion kilometers). Nothing traveling through space is faster. To put that into perspective: In the time it takes you to blink your eyes, a particle of light travels around the circumference of the Earth more than twice.

As incredibly fast as that is, space is incredibly spread out. Light from the Sun, which is 93 million miles (about 150 million kilometers) from Earth, takes just over eight minutes to reach us. In other words, the sunlight you see is eight minutes old.

Alpha Centauri, the nearest star to us after the Sun, is 26 trillion miles away (about 41 trillion kilometers). So by the time you see it in the night sky, its light is just over four years old. Or, as astronomers say, it's four light years away.

Related: The shape of light: Scientists reveal image of an individual photon for 1st time ever

With those enormous distances in mind, consider Cristina's question: How can light travel across the universe and not slowly lose energy?

Actually, some light does lose energy. This happens when it bounces off something, such as interstellar dust, and is scattered about.

But most light just goes and goes, without colliding with anything. This is almost always the case because space is mostly empty – nothingness. So there's nothing in the way.

When light travels unimpeded, it loses no energy. It can maintain that 186,000-mile-per-second speed forever.

It's about time

Here's another concept: Picture yourself as an astronaut on board the International Space Station. You're orbiting at 17,000 miles (about 27,000 kilometers) per hour. Compared with someone on Earth, your wristwatch will tick 0.01 seconds slower over one year.

That's an example of time dilation – time moving at different speeds under different conditions. If you're moving really fast, or close to a large gravitational field, your clock will tick more slowly than someone moving slower than you, or who is further from a large gravitational field. To say it succinctly, time is relative.

Now consider that light is inextricably connected to time. Picture sitting on a photon, a fundamental particle of light; here, you'd experience maximum time dilation. Everyone on Earth would clock you at the speed of light, but from your reference frame, time would completely stop.

That's because the "clocks" measuring time are in two different places going vastly different speeds: the photon moving at the speed of light, and the comparatively slowpoke speed of Earth going around the Sun.

What's more, when you're traveling at or close to the speed of light, the distance between where you are and where you're going gets shorter. That is, space itself becomes more compact in the direction of motion – so the faster you can go, the shorter your journey has to be. In other words, for the photon, space gets squished.

Which brings us back to my picture of the Pinwheel galaxy. From the photon's perspective, a star within the galaxy emitted it, and then a single pixel in my backyard camera absorbed it, at exactly the same time. Because space is squished, to the photon the journey was infinitely fast and infinitely short, a tiny fraction of a second.

But from our perspective on Earth, the photon left the galaxy 25 million years ago and traveled 25 million light years across space until it landed on my tablet in my backyard.

And there, on a cool spring night, its stunning image inspired a delightful conversation between a nerdy scientist and his curious wife.

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

Scientists have found evidence of a previously-undetected dwarf planet at the edge of the solar system.

The object, dubbed 2017 OF201, follows an extreme, oblong orbit, taking some 25,000 Earth years to circle the sun. The findings, which were confirmed by the International Astronomical Union's Minor Planet Center but have not yet been peer reviewed, were published May 21 on the preprint server arXiv.

2017 OF201 is a roughly spherical body about 435 miles (700 kilometers) in diameter, lurking beyond Neptune's orbit. A team of scientists spotted it while poring through archival data from the Blanco telescope in Chile and the Canada-France-Hawaii telescope based in Hawaii. The researchers tracked the object's motion across 19 sets of images spanning seven years.

At its closest, the dwarf planet orbits at nearly 45 AU, or 45 times the distance from Earth to the sun — a similar distance as its fellow dwarf planet Pluto. Based on the newfound object's trajectory, the scientists estimate its last close pass to the sun was in 1930, the same year Pluto was discovered. It's now twice as far away and rocketing off even further into space. At its farthest point, 2017 OF201 will be a whopping 1,600 AU before starting its journey back inward.

This oblong orbit hints at complex gravitational interactions, both with Neptune and with the pull of the Milky Way's gravity.

"There may have been more than one step in its migration," study co-author Sihao Cheng, an astrophysicist at the Institute for Advanced Study in Princeton, New Jersey, said in a statement. "It's possible that this object was first ejected to the Oort cloud, the most distant region in our solar system, which is home to many comets, and then sent back."

Related: Planet Nine: Is the search for this elusive world nearly over?

Because it's so difficult to spot solar system objects this far away, it's possible 2017 OF201 isn't the only dwarf planet waiting to be discovered.

"2017 OF201 spends only 1% of its orbital time close enough to us to be detectable," Cheng said. "The presence of this single object suggests that there could be another hundred or so other objects with similar orbit and size; they are just too far away to be detectable now."

The newly-discovered object could also challenge theories of Planet 9, a proposed but unobserved large planet orbiting billions of miles beyond Neptune. Some scientists have proposed the influence of Planet 9's gravity to explain the clustered orbits of some trans-Neptunian objects. But 2017 OF201 doesn't fit neatly into this observed pattern, and the researchers suggest that the gravitational pull of Planet 9 — if it exists — would knock 2017 OF201 out of the solar system fairly quickly. Further observations will be needed to better understand these possible interactions, the team wrote in the study.

"Even though advances in telescopes have enabled us to explore distant parts of the universe, there is still a great deal to discover about our own solar system," Cheng said.

Jupiter, the solar system's largest planet, used to be even bigger, according to a new study.

The cloud of gas and dust from which the sun and planets formed dissipated around 4.5 billion years ago. At that time, Jupiter was at least twice its current size, and its magnetic field was about 50 times stronger, researchers found. The findings, which the team described in a study published May 20 in the journal Nature Astronomy, could help scientists develop a clearer picture of the early solar system.

"Our ultimate goal is to understand where we come from, and pinning down the early phases of planet formation is essential to solving the puzzle," study co-author Konstantin Batygin, a planetary scientist at Caltech, said in a statement. "This brings us closer to understanding how not only Jupiter but the entire solar system took shape."

Jupiter's immense gravity — along with the sun's — helped fashion the solar system, shaping the orbits of other planets and rocky bodies. But how the giant planet itself formed remains opaque.

To gain a better picture of Jupiter's early days, the researchers studied the present-day, slightly tilted orbits of two of Jupiter's moons, Amalthea and Thebe. The paths these moons chart are similar to what they were when they first formed, but the moons have been pulled slightly over time by their larger, volcanically active neighbor Io. By analyzing the discrepancies between the actual changes and those expected from Io's nudges, the researchers could work out Jupiter's original size.

Related: 'This has left us scratching our heads': Astronomers stumped by James Webb telescope's latest views of Jupiter

When the solar nebula dissipated, marking the end of planet formation, Jupiter's radius would have been between two and 2.5 times its current size to give Amalthea and Thebe their current orbits, the scientists calculated. Over time, the planet has shrunk to its current size as its surface cools. Then, the team used the radius to calculate the strength of the planet's magnetic field, which would have been around 21 milliteslas — about 50 times stronger than its current value and 400 times stronger than Earth's.

"It's astonishing that even after 4.5 billion years, enough clues remain to let us reconstruct Jupiter's physical state at the dawn of its existence," study co-author Fred Adams, an astrophysicist at the University of Michigan, said in the statement.

The findings sharpen researchers' view of the solar system at a critical transition point in its history. The calculations also don't depend on how Jupiter formed — a process that's still not understood in detail — relying instead on directly observable quantities.

"What we've established here is a valuable benchmark," Batygin said in the statement. "A point from which we can more confidently reconstruct the evolution of our solar system."

Jupiter is currently shrinking by about 2 centimeters per year, according to Caltech. This is due to the Kelvin-Helmholtz mechanism — a process by which planets grow smaller as they cool. As Jupiter slowly cools, its internal pressure drops, causing the planet to steadily shrink. It's unclear when this process began.

Earth's minimoon may be a chip off the old block: New research suggests that 2024 PT5 ​​— a small, rocky body dubbed a "minimoon" during its discovery last year — may have been blown off the moon during a giant impact long ago, making it the second known sample traveling near Earth's orbit.

The discovery hints at a hidden population of lunar fragments traveling near Earth.

"If there were only one object, that would be interesting but an outlier," Teddy Kareta, a planetary scientist at Lowell Observatory in Arizona, said in March at the 56th annual Lunar and Planetary Sciences Conference in the Woodlands, Texas. "If there's two, we're pretty confident that's a population."

A new kind of evidence

Earth travels through and with a cloud of debris as the planet makes tracks around the sun. Some of that material is human-made — satellites and space junk. Other material is rocky debris left over from collisions in the early solar system. These near-Earth objects (NEOs) can be a concern, so they are tracked to ensure they are not a threat to our planet.

Related: Potentially hazardous asteroids: How many dangerous space rocks lurk near Earth — and can we stop them?

In August 2024, astronomers in South Africa identified a new rock, known as 2024 PT5, traveling near Earth. 2024 PT5 was moving slowly, with a relative velocity of only 4.5 mph (2 meters per second), making it a strong target for the Mission Accessible Near-Earth Object Survey (MANOS). Only nine other asteroids have been seen traveling so slowly at their closest approach.

Kareta, along with MANOS principal investigator Nick Moskovitz, also at Lowell, have been intrigued by the idea of finding moon rocks in space since just after the first such fragment was identified in 2021. MANOS is designed to hunt for and characterize the near-Earth asteroids that might be the easiest to visit with a spacecraft. According to Kareta, that meant the survey was ideal for looking at lunar castoffs. Within a week of 2024 PT5's discovery, they had turned the Lowell Discovery Telescope in the space rock's direction.

After studying 2024 PT5 in both visible and near-infrared data, they concluded that it wasn't an ordinary asteroid. Its composition proved similar to that of rocks carried back to Earth during the Apollo program, as well as one returned by the Soviet Union's Luna 24. The researchers also found that 2024 PT5 was small — 26 to 39 feet (8 to 12 meters) in diameter.

Kareta and his colleagues suspect that 2024 PT5 was excavated when something crashed into the moon. By studying the asteroid's composition, they hope to tie the material back to its source and perhaps even identify its parent crater.

Cratering events are one of the most important processes that shape planetary bodies without tectonics or liquids to remold them. But impacts can be affected by a variety of variables, and understanding them can be a challenge. Matching debris to its crater can provide another way to understand what happens when two bodies collide. That's what makes identifying lunar rocks in space so intriguing.

"It's like realizing a crime scene has a totally new kind of evidence you didn't know you had before," Kareta told Space.com by email. "It might not help you solve the crime right away, but considering the importance of the task, new details to compare are always welcome."

Changing lanes

Material from the Earth-moon system should be some of the easiest to fall into orbit near Earth. After an impactor collides with the moon, all but the fastest-moving material flung into space should continue traveling near our system. Although 2024 PT5 was dubbed a minimoon in September, it only briefly fell in line with the planet.

Kareta compared it to two cars on the highway. Earth is blazing along in its own lane, while 2024 PT5 chugged along the interior path, closer to the sun. In 2024, the tiny chunk of rock changed lanes, falling into Earth's path at roughly the same speed. By the end of September, it had moved on, shifting outward. Earth left it behind, but on the solar race track, the pair should be parallel again in 2055, scientists estimate.

2024 PT5 is the second lunar fragment identified by researchers. Another small rock, Kamo'oalewa, was traced to the moon in 2021, five years after its discovery. That could hint at a new population, hidden in plain sight.

Both objects are traveling in Earth-like orbits, but they don't have much else in common. Kamo'oalewa is larger and appears to have been battered by cosmic rays, solar radiation and other processes longer than 2024 PT5 has. That might suggest it has been in space longer, Kareta said.

Their orbits are also a bit different. Kamo'oalewa's quasi-satellite orbit keeps it in Earth's immediate vicinity for several consecutive orbits, even though it isn't actually spinning around the planet. Unlike the lane-changing 2024 PT5, Kamo'oalewa is more like a car that stays one lane over, moving at roughly the same speed.

Researchers are trying to match Kamo'oalewa to a crater. A recent study suggested that it could have come from a smashup that created Giordano Bruno crater, a 14-mile-wide (22 km) impact basin on the far side of the moon.

Kareta is hopeful that more will be identified. While a single sample is an oddity, two could be part of a crowd. He suspects that some asteroids that have been identified as unusual may be lunar rocks in disguise.

When the orbits of NEOs are calculated, their source region is often estimated based on their current travels. If some objects have been misclassified and their sources are incorrect, that could mean other aspects of their orbits are misunderstood. Although that could potentially increase the long-term chances of Earth being hit by an asteroid, Kareta said it is "almost certainly not" the case, "but we'll need to prove it."

For now, Kareta and his colleagues will continue to use MANOS to search for other potential lunar fragments. He's hopeful that the doubled population will convince other researchers to take a closer look, too. Upcoming large-scale surveys — like the Vera Rubin Observatory, a ground-based telescope expected to see first light this year — should also help to reveal other dim objects.

The research was published in January in The Astrophysical Journal Letters.

Originally posted on Space.com.

Astronomers searching for a ninth planet in our solar system say they've found a "good" candidate far beyond Neptune, according to a new preprint study.

This could be humanity's first glimpse at the long-theorized Planet Nine, which — if it exists — is a giant, undiscovered world distantly orbiting our sun. However, the ninth planet proposal is contentious, and the new findings are unlikely to change that.

Researchers discovered this latest planetary candidate while studying old satellite data. At this stage, the candidate is simply a curious dot across a few infrared images. But the dot seemed to be moving in a way that was consistent with a large, distant planet.

"I felt very excited," study lead-author Terry Phan, an astronomy doctoral student at the National Tsing Hua University in Taiwan, told Science, recalling the discovery. "It's motivated us a lot."

Phan and his colleagues posted their findings to the preprint server arXiv on April 24, which have been accepted for publication in the journal Publications of the Astronomical Society of Australia. However, the preprint has been met with some skepticism.

Mike Brown, an astronomer at Caltech who first proposed the Planet Nine hypothesis with a colleague in 2016, isn't convinced that the infrared dots correspond to the elusive planet. Brown wasn't involved in the study, but calculated the orbit of the infrared signal and found that the object would be tilted about 120 degrees from the Solar System's plane, Science reported. That tilt is much greater than Planet Nine's predicted tilt of around 15 to 20 degrees, and also means this object would be orbiting in a different direction from the known planets, which all sit roughly on the same plane.

This mismatch "doesn't mean it's not there, but it means it's not Planet Nine," Brown told Science. "I don't think this planet would have any of the effects on the Solar System that we think we're seeing."

Related: How long would it take to reach Planet 9, if we ever find it?

The predicted position of Planet Nine is meant to explain the irregular orbits of some objects in the Kuiper Belt at the far reaches of our solar system. However, some researchers are unconvinced that these orbits are caused by an undiscovered planet, and the scientific community as a whole is still waiting for any direct observational evidence of Planet Nine's existence.

If Planet Nine does exist, then researchers have predicted that it's much larger than Earth and orbits in an unusual pattern billions of miles beyond Neptune — the eighth and, as things stand, final planet in our solar system. Planet Nine's supposed orbit is so far away from the sun that it would be difficult for Earthling scientists to detect, hence why they're having a hard time proving or disproving its existence.

The team behind the new study searched for Planet Nine candidates in the data archives of two decommissioned satellites: the 1983 Infrared Astronomical Satellite (IRAS) and the 2006-2011 AKARI satellite, Live Science's sister site Space.com reported. They were looking for distant objects that moved slowly between one set of data and the next, like the proposed Planet Nine would be doing if it were orbiting our sun.

After ruling out the known objects in the data, the researchers zeroed in on a shortlist of candidates. They then pored over images of these potential objects and eventually came away with what they described in the study as "one good candidate." The candidate is a dot with the same colors and brightness across the two sets of images, suggesting it's one object captured by both satellites. Follow-up observations are needed to determine the object's full orbit, according to the study.

Brown told Science that if the infrared signal is a planet, then based on his calculations, it couldn't exist alongside the original hypothesized Planet Nine without the two making each other's orbits unstable. Thus, the new candidate for Planet Nine could be a different planet with the potential to disprove the Planet Nine hypothesis.

The existence of Planet Nine — or any other undiscovered ninth planet in our solar system — will likely remain a contentious subject for now. However, 2025 could prove to be the beginning of the end for the search.

The Vera C. Rubin Observatory, currently under construction in Chile, will open later this year and has the potential to settle the Planet Nine debate. This state-of-the-art observatory will feature the world's largest digital camera and look deeper into space than its predecessors. Researchers are hoping it will be able to spot Planet Nine within a year or two, if it's out there at all.

Constant gusts of particles from the sun may be creating water molecules on the moon, a new NASA-led experiment hints.

Scientists have detected traces of water molecules — as well as hydroxyl (OH) molecules, a component of water — on the surface of the moon through multiple space missions. The source of this water has long been a mystery, though some theories suggest volcanism, outgassing from deeper in the lunar regolith (the combination of rock and dust on the surface of the moon), and bombardment by tiny meteorites.

The new NASA experiment, described March 17 in the journal JGR Planets, tests a different idea: that solar wind is behind it all.

Solar wind is a constant gale of charged particles streaming from the sun at over 1 million mph (1.6 km/h). It bombards everything in the solar system, including Earth, and causes colorful auroras when it collides with molecules in our atmosphere. Our planet's magnetosphere shields us from the brunt of this space weather. The moon, however, has a very weak and splotchy magnetic field, so it is less protected.

Water is made up of hydrogen and oxygen atoms. The rocks and dust making up the surface of the moon contain a lot of oxygen but not a lot of hydrogen. Solar wind is mostly made of protons, which are hydrogen atoms missing their electrons. Without a strong magnetic field to protect it, the solar wind slams into the moon's surface every day, seeding it with protons that steal or borrow electrons from the lunar regolith to form the hydrogen needed to make water.

Related: Earth's moon could've had Saturn-like rings, new study hints

According to NASA, the water that's been detected on the moon follows an interesting pattern — it changes on a daily cycle. Areas warmed by the sun release water as vapor, while colder regions hold onto it. If the source of water was something like micrometeorite collisions, we might expect the water to keep decreasing in warm areas until more impacts occur. However, the amounts of water detected return to the same levels every day, even as some of it is lost to space. This makes it more likely that solar wind is involved.

To test this theory, the researchers simulated the effects of solar wind striking the moon using samples of lunar regolith collected by Apollo 17 astronauts in 1972. They built a tiny particle accelerator in a vacuum to launch "mock solar wind" at the samples for multiple days, simulating the effects of the real solar wind hitting the moon for 80,000 years. Then, they measured how the chemical makeup of the sample had changed — and it showed evidence of water that wasn't there before.

"The exciting thing here is that with only lunar soil and a basic ingredient from the Sun, which is always spitting out hydrogen, there's a possibility of creating water," study lead author Li Hsia Yeo, a planetary scientist at NASA's Goddard Space Flight Center, said in a statement.

Understanding how water forms on the moon is important for future astronaut missions, the researchers said. Water ice stored at the lunar south pole could be an important resource for astronauts, for example.

The results also provide insight into the solar wind's interactions beyond the moon. Other celestial bodies that don't have much of an atmosphere or a magnetic field are also bombarded by solar wind, so studying how these environments change can help us understand celestial chemical processes that generate or strip away water, a key building block for life.