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?

Molecular vibrations can "catapult" electrons across solar materials in quadrillionths of a second‬ ‪— much faster than previously thought, a new study shows.

The findings could help scientists find more efficient ways to convert solar energy into electricity, according to the study, which was published March 5 in the journal Nature Communications.

"We're effectively watching electrons migrate on the same clock as the atoms themselves," study co-author Pratyush Ghosh, a researcher who studies ultrafast spectroscopy at the University of Cambridge, said in a statement.

Organic molecules go solar

Organic solar cells use carbon-based molecules, rather than silicon, to convert sunlight into electricity. In theory, organic solar cells could provide that electricity at lower cost than conventional solar cells, but they are much less efficient.

In a typical organic solar cell, an electron donor and an electron acceptor are sandwiched between two conductive electrodes. When light hits the cell, it generates an "exciton," an electron-hole pair. Excitons split at the interface between the donor and the acceptor, generating electricity.

To achieve fast charge transfer at the interface and limit energy loss, the donor and acceptor molecules usually have strong electronic coupling, or overlap between their electronic states, which allows charges to move easily between molecules. They also often have a large energy difference between them, but that limits the voltage available from the device.

In the new study, researchers observed ultrafast charge transfer at a junction between the electron donor and electron acceptor in an organic solar cell, without needing to conform to either of these constraints. The team used a short laser pulse to excite the electron donor, a polymer called TS-P3, and then used a different laser to measure how the system changed during charge transfer.

That charge transfer happened in 18 femtoseconds ‪—‬ about as fast as an individual molecule vibrates. A few other systems without strong driving forces exhibit charge transfer over 100 to 200 femtoseconds, but most take ten to a thousand times that long.

"Seeing it happen on this timescale within a single molecular vibration is extraordinary," Ghosh said in the statement.

A 'molecular catapult'

That similar timescale wasn't a coincidence. In a second set of laser experiments, the team found that vibrations in the polymer donor molecule launched an electron across the junction to an acceptor molecule. When the electron arrived, it triggered overlapping vibrations in the acceptor molecule. This overlap allowed charge transfer to happen much more quickly than expected, and without the need for strong coupling or a large energy difference.

"Instead of drifting randomly, the electron is launched in one coherent burst," Ghosh said in the statement. "The vibration acts like a molecular catapult. The vibrations don't just accompany the process, they actively drive it."

The findings help to explain the processes that control the speed of charge transfer and establish new strategies for designing more efficient organic solar cells and materials, the researchers wrote in the study.

"Instead of trying to suppress molecular motion, we can now design materials that use it ‪—‬ turning vibrations from a limitation into a tool," study co-author Akshay Rao, a physicist at Cambridge, said in the statement.

Researchers have developed a technology to invisibly transmit information disguised as background thermal radiation. Using a phenomenon called "negative light," they transferred 100 kilobits of data per second in a way that was completely undetectable to outside observers.

Most methods for concealing data during transfer involve hiding it among other data or encrypting it in a way that makes it impossible to read without a cipher or other means of decryption. The new technique, by contrast, makes the data almost impossible to intercept because there's no indication it's being sent at all. It can also be encrypted through traditional means to further harden security, the team wrote in a paper published March 5 in the journal Light: Science & Applications.

This hidden transfer is possible due to a phenomenon called "negative light." It relies on infrared radiation, which is the band just beyond the red end of the visible light spectrum. Infrared radiation is invisible to the naked eye, but it can be detected with thermal cameras. We experience it as heat from warm objects, and all objects emit a faint glow in the infrared.

The negative luminescence the team used could make that glow dimmer, rather than brighter. In a statement, Michael Nielsen, a professor of engineering at the University of New South Wales Sydney and lead author of the study, compared it to a flashlight that could "project darkness" as compared to background light, rather than simply turning off.

Using devices called thermoradiative diodes, the team created patterns of brighter- or darker-than-usual states that blended into typical infrared background "noise" but that can be read as data by specialized receivers.

The thermoradiative diodes were born as part of another project, in which the team proved that it was possible to generate solar power even after the sun had set. This "night-time solar" tech captured infrared radiation that Earth had absorbed during the day and was releasing at night as it cooled. The team then used thermoradiative diodes to generate a small amount of power.

While the initial transfer rate of 100 kbps is quite modest, Nielsen said higher speeds are achievable. The main hurdle was the availability of some of the sophisticated electronics the team required. In principle, there's nothing stopping this method from transferring tens of megabits per second with existing devices, with better devices and detector design pushing the speed to gigabits per second, the team said.

In fact, a commercial product delivering megabit-per-second data rates may be possible in just a few years, Ned Ekins-Daukes, a professor of photovoltaic and renewable energy engineering at UNSW and co-leader of the research, said in the statement.

By using graphene ‪—‬ a single-atom-thick sheet of carbon atoms arranged in a honeycomb pattern ‪—‬ instead of the current semiconductor material in the diodes, "we can potentially achieve data transfer rates in the gigabits-per-second range, if not hundreds of gigabits," Ekins-Daukes said.

Improved data security would have major applications in a variety of industries, including health care, defense, finance and manufacturing. Nielsen believes that virtually any communication that could benefit from security beyond standard encryption could take advantage of his team's breakthrough.

"The real advantage of this technique is that the very signal or act of communication is hidden if an outside observer doesn't have the same technology required to intercept the communication," Nielsen told Live Science in an email.

Astronomers have produced one of the most accurate, comprehensive cosmic maps ever made, revealing a brilliant "sea of light" that permeated the early universe.

Unlike other universal maps, this 3D representation is composed of light emitted by a single element: hydrogen, the simplest and most abundant element in the universe, which emits large quantities of a specific wavelength of light when it becomes excited by energy from nearby stars.

By measuring this light across a vast patch of sky, astronomers got a glimpse of what the universe looked like 9 billion to 11 billion years ago, during an epoch of vigorous star formation.

The new research, described in a paper published March 3 in The Astrophysical Journal, is part of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), a sky survey that aims to illuminate how dark energy and gravity shape the universe. The researchers can now compare their simulations with this new data, gathered with the Hobby-Eberly Telescope at the McDonald Observatory in Texas, to assess how cosmological models differ from observations.

An exciting way to see the baby universe

When hydrogen atoms are bombarded by stellar radiation, they become excited and emit Lyman-alpha light, a specific wavelength in the ultraviolet part of the electromagnetic spectrum.

Massive, bright galaxies are easier to detect, but fainter galactic structures and the immense interstellar gas clouds that form stars and galaxies have remained largely undetected — until now.

To reveal the sea of light that permeated the fledgling cosmos, the researchers used a technique called line-intensity mapping, which focuses on the telltale wavelengths, or signature spectral emissions, given off by different elements. Astronomers can therefore use line mapping to chart the concentration and distribution of those specific elements throughout the cosmos, forming a map of the luminous galaxies and glowing gas clouds lit up by excited hydrogen atoms.

Cosmology is about zooming out

When studying individual galaxies, stars or other discrete celestial objects, astronomers analyze their characteristics by zooming in. Cosmology, however, requires zooming out. Accordingly, the HETDEX survey doesn't observe individual galaxies but rather the combined light from every object in a designated region of the sky. As a result, astronomers can gather integrated data from a multitude of galaxies and intergalactic gas clouds simultaneously.

"Imagine you're in a plane looking down," study co-author Julian Muñoz, a theoretical cosmologist at The University of Texas at Austin, said in a statement. "The 'traditional' way to do galaxy surveys is like mapping the brightest cities only: you learn where the big population centers are, but you miss everyone that lives in the suburbs and small towns. Intensity mapping is like viewing the same scene through a smudged plane window: you get a blurrier picture, but you capture all the light and not just the brightest spots."

In the quest to understand dark energy and chart more than 1 million bright galaxies, HETDEX "has gathered more than 600 million spectra over an area equivalent to more than 2,000 full moons, creating an unprecedented dataset," the researchers said in a different statement.

A golden age of cosmic mapping

The mapping method made possible by HETDEX offers another way to examine cosmology’s driving forces and how mass is distributed throughout the universe.

"These new 3D maps allow us to study how galaxies cluster together," study co-author Karl Gebhardt, a professor of astrophysics at The University of Texas at Austin, told Live Science via email. "The culprit that causes galaxies to come together is gravity. So by studying the clustering properties, we are understanding the properties of gravity and how much mass exists," Gebhardt explained.

Seeing galactic structures as a collective is invaluable for measuring large-scale density fluctuations across the cosmos to explore the influence of dark energy, the mysterious entity that appears to be accelerating the universe's expansion.

Unsurprisingly, detecting the signals from ancient galaxies is hard, "but excluding the faint signal from everything else — faint galaxies in the foreground, noise from the detector, artifacts produced by the analysis techniques, scattered light sources like the moon, weak absorption/emission lines from the Earth's atmosphere, is even harder," study co-author Robin Ciardullo, a professor of astronomy and astrophysics at Penn State and the observing manager of HETDEX, told Live Science via email.

The next step is to improve noise-reduction techniques and separate the desired signals from the numerous astronomical and Earthly contaminants. The researchers can then use fainter sources and lower-mass objects as tracers of cosmic evolution to more robustly constrain gravity models.

"The Hobby-Eberly is a pioneering telescope," Muñoz said. "And with new, complementary instruments coming online, we’re entering a golden age for mapping the cosmos."

Look into the night sky, and it might seem like space is a vast expanse of darkness. But are any regions darker than others? What's the darkest place in the solar system and, on a grander scale, the universe?

In short, the answer isn't straightforward, and it depends on whom you ask, experts told Live Science.

True darkness, the blackest black, is surprisingly rare and hard to pinpoint. This is because there is a lot of dust in the cosmos: Dust scatters light, making space glow far beyond stars, Marc Postman, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, told Live Science. As a result, there is a background glow that permeates much of the universe. (The color of the universe is actually "cosmic latte," a beige shade not too far off white.)

Darkness also "depends on how you define it," Andreas Burkert, a theoretical astrophysicist at the University of Munich, told Live Science. The visible light spectrum illuminates some places in the universe with light. However, other wavelengths on the electromagnetic spectrum, like gamma rays and ultraviolet light, touch almost everything. This means that space, when viewed in the full electromagnetic spectrum, is quite luminous.

Low albedos

If you consider only visible light, there are some exceedingly dark places in space. A number of factors contribute to this darkness.

Firstly, cosmic objects can be made of light-absorbing material, making them appear very dark. Scientifically, this is known as albedo, or the amount of light reflected off a surface. A perfect mirror, for instance, would reflect 100% of the light directed at it and have an albedo of 1, while charcoal has an albedo of 4%.

The nucleus of comet Borrelly (also called 19P/Borrelly) is one of the darkest spots in our solar system, according to the Guinness Book of World Records. The 5-mile-long (8 kilometers) comet is made up of dust and ice that reflects less than 3% of sunlight, based on an image taken in 2001.

Similarly, the darkest known exoplanet in the universe, TrES-2 b, reflects less than 1% of light, thought to be because of high amounts of sodium vapors and gaseous titanium oxide in the atmosphere. In contrast, Earth reflects about 30% of the sun's light.

Black holes, too, are dark because they capture light that crosses the event horizon. But interestingly, "that doesn't mean that there is no light," Burkert said. "It simply is trapped." As a result, "when you enter the black hole, it's actually extremely bright," he explained.

Blocking light and distant objects

Darkness can also exist if something is blocking light from nearby stars. For example, some craters on our moon, located at the poles, never see the sun's light. These places are very dark because they are in "permanent shadow," Postman said. The shadowed craters on Pluto can be quite dark as well, because of their distance away from the sun.

Far beyond that, dense dust clouds, called molecular cores or Bok globules, are also thought to be pitch black. They look like "a hole in the sky," Burkert said. This is because the globule, made up of a mix of molecular hydrogen, carbon oxides, helium and silicate dust, blocks nearly all visible light from surrounding stars, making them disappear. However, this light-blocking is not as profound in the infrared spectrum, Burkert noted, who has studied Barnard 68, a globule around 500 light-years away from Earth.

Finally, there are pockets of the sky that are dark simply because they are far away from any light source. These places were documented by NASA's New Horizons telescope, an instrument sent to take photos of the galaxy's outer corners.

Based on a 2021 paper published in The Astrophysical Journal, these faraway regions are very dark. "On average, the sky out there is 10 times darker than it is near the Earth," said Postman, who was a co-author on the study. However, these regions still had light from the background glow of the cosmos.

Burkert noted the Earth sits in a relatively dark cavity in the Milky Way, which uniquely allows us to have an unobstructed view far into space.

"We sit in the middle of this big bubble, and so we can see a lot of stars," Burkert said. "If we would not be in the bubble, maybe astronomy would not have developed. So [darkness] is a very relevant, I think, important idea and question."

On the night of April 19, 1787, astronomer William Herschel noted an hours-long light as bright as the Orion Nebula emanating from the unlit, new moon. He had likely witnessed a "transient lunar phenomenon" (TLP) — a short-term change in the appearance of part of the lunar surface.

TLPs include brightening, reddish or violet blotches and foggy spots. In fact, some 3,000 TLPs have been documented over the past two millennia by people wielding telescopes, cameras or just plain good vision, said Anthony Cook, a research lecturer in physics at Aberystwyth University in the U.K.

But what causes these strange flashes on the moon? While a plethora of physical phenomena can produce TLPs, the duration of a specific TLP, which may range from milliseconds to hours, can hint at its cause, experts told Live Science.

From milliseconds to hours

Superfast flickers — those that last less than a minute — likely occur due to meteoroid strikes, Masahisa Yanagisawa, a professor emeritus at the University of Electro-Communications in Japan, told Live Science in an email. Meteoroids heavier than 0.44 pounds (0.2 kilograms) — about the weight of a billiard ball — produce fleeting flashes of light upon striking the lunar surface. The flashes themselves come from the energy of the impacts that heat rocks on the lunar surface, causing them to glow until they cool.

While such lunar impact flashes (LIFs) were long suspected to be the flickers, scientists couldn't definitively identify them until in the 1990s, when high-speed video cameras became readily available for lunar monitoring, Yanagisawa said. Yet even then, he added, the flashes' short duration meant that factors like electric noise within the cameras couldn't be ruled out.

Confirming a flash, therefore, involved simultaneous observations from two or more distant locations. Despite these constraints, Yanagisawa said, "some flashes were first confirmed during the Leonid meteor shower in November 1999," which he documented in a 2002 study published in the journal Icarus.

Since then, hundreds more LIFs have been formally recorded by projects like the European Space Agency-funded Near-Earth Object Lunar Impacts and Optical Transients (NELIOTA) program. NELIOTA has recorded 193 LIFs over nine years, and a map of these suggests the flashes occur in specific hotspots, like the Oceanus Procellarum, a lunar region that is potentially tectonically active.

However, the project's principal investigator, Alexios Liakos, an associate researcher at the National Observatory of Athens, said this apparent pattern is an observational bias. In fact, a 2024 study he co-authored showed that the moon is pummeled "almost homogeneously by meteoroids," he told Live Science in an email.

In contrast, lunar lights that last minutes may originate in radon gas released from the moon's interior. A pair of studies published in 2008 and 2009 in The Astrophysical Journal suggest that such outgassing occurs when accumulated gas below the moon's surface is explosively released by triggers like "moonquakes." The radioactive radon generates light upon decaying, making it visible from Earth. Plus, spots where longer-lasting lights were observed largely overlap with areas with high concentrations of radon.

But some lights on the moon — like the kind witnessed by Herschel — last hours. Such sightings may be indirectly associated with the moon, according to a 2012 study. The study suggested that the solar wind — the stream of charged particles emanating from the sun — ionizes lunar dust particles, kicking them into enormous clouds 62 miles (100 kilometers) high. These clouds may refract light from stars or other bright objects that appear close to the moon in the sky, ostensibly lighting the lunar surface.

However, some researchers, like Liakos, dispute the existence of long TLPs. "The only longer (and not long) events that I have observed are satellites that cross the lunar disk," Liakos said, adding that he hasn't seen any long-lasting TLPs while observing the moon's night side since 2017.

Still, if you ever see a light on the moon, take note. It could be an illusion of light reflecting off a satellite — but there's a good chance it's a TLP.

Moon quiz: What do you know about our nearest celestial neighbor?

Nowadays, the dark of night is interspersed with the light of stars. But before the stars were born, did light shine at the beginning of the universe?

The short answer is "no." But the long answer reveals light's extraordinary journey. At first, the early universe's light was "trapped," and it took several hundred thousand years for it to escape. Then, it took about 100 million years for stars to form.

By examining the speed and direction in which galaxies were moving, astronomer Edwin Hubble discovered the universe was expanding. This 1929 discovery suggested that the cosmos was once smaller, with scientists eventually calculating that the entire universe was concentrated into one, infinitely dense point about 13.8 billion years ago, until the Big Bang happened.

"With the Big Bang, space was created and expanded, along with everything in the universe," Andrew Layden, chair of physics and astronomy at Bowling Green State University in Ohio, told Live Science.

The only way all the matter that now makes up the universe could fit in a tiny spot "is if it was energy at that time," Layden said. Einstein's famous equation E=mc² revealed that energy and mass can be interchangeable, Layden explained.

As the universe expanded, the density of its energy decreased, and it cooled. The first particles then began to form within the first second after the Big Bang, according to Las Cumbres Observatory. These included the photons that make up light, as well as the protons, neutrons and electrons that make up atoms. By about three minutes after the Big Bang, protons and neutrons could fuse together to create the nuclei of atoms such as helium, according to NASA.

"Think of fog and dew," Layden said. "Particles in a high-energy state are dispersed like water in fog, and when the energy gets low enough, they can condense out like droplets of dew."

Related: Can anything travel faster than the speed of light?

However, although photons of light existed since the first second after the Big Bang, they could not yet shine across the universe. This is because the early cosmos was so hot that "electrons were moving too fast for atomic nuclei to hold them in orbit around them," Layden said. "The universe was just this very hot, dense soup."

All the electrons zipping around freely in the early universe meant that light could not move around very much. "As light tried to travel in a straight line during this time, it always bumped into electrons, so it could not go very far," Layden said.

A similar situation is found within the sun, Srinivasan Raghunathan, a cosmologist at the University of Illinois, Urbana-Champaign, told Live Science. "You can imagine a photon of light created by nuclear reactions at the center of the sun trying to come out to the sun's surface," he said. "The center of the sun is extremely hot, and so there are a lot of free electrons present. This means light cannot travel in straight lines."

The distance from the center of the sun to its surface is about 432,450 miles (696,000 kilometers). The speed of light in a vacuum is about 186,000 miles per second (300,000 km/s), but in the sun, "it takes about 1 million to 2 million years for light to escape from the center of the sun to its surface," Raghunathan said.

However, about 380,000 years after the Big Bang, the expansion of the universe let the cosmos cool enough for atomic nuclei to glom onto electrons. "When that happens, all those electrons are no longer free," Layden said. "This happens at about 3,000 Kelvin [4,940 degrees Fahrenheit, or 2,725 degrees Celsius], the surface temperature of a coolish reddish star."

Within a short number of years, "everything goes from being a hot dense soup to a clear universe where light can travel freely," Layden said. "At that moment, the first photons in the universe can escape."

The light typical of the universe when it was about 3,000 kelvins was in near-infrared to visible wavelengths, Layden noted. However, as the cosmos expanded over the course of more than 13 billion years and cooled to an average temperature of about 2.73 Kelvin (minus 455 F, or minus 270 C), the universe's first light stretched to longer microwave wavelengths.

Astronomers first detected this leftover radiation from the Big Bang, called the cosmic microwave background, in 1964.

Analyzing these microwaves has yielded many insights. For instance, the gravitational pull of galaxies can distort light — a phenomenon called gravitational lensing. Examining the amount of distortion the cosmic microwave background has experienced at different points in the sky can help scientists reconstruct the large-scale structure of the universe — the arrangement of galaxies and the giant voids between them across the cosmos, Raghunathan said.

After the light from the Big Bang was released, the universe experienced a period known as the cosmic dark ages. Eventually, after millions of years, the gravitational pull of clouds of gas led these clumps of matter to collapse in on themselves.

"This created the first generation of stars, and the universe had galaxies full of stars by about 1 billion years after the Big Bang, beginning the cosmic dawn," Layden said.

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

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.

A massive streak of white, aurora-like light recently appeared in the night sky above several U.S. states after a Chinese rocket released half a dozen satellites into orbit. The light show was triggered when the rocket dumped a new type of fuel into space before reentering the atmosphere, experts say.

The luminous streak appeared at around 1:24 a.m. ET on Saturday (May 17), hanging in the air for around 10 minutes before eventually fading away. It was photographed in at least seven states — Colorado, Idaho, Utah, Missouri, Nebraska, Washington and New Mexico — but may have been visible even further afield, according to Spaceweather.com.

Photographer Mike Lewinski snapped stunning shots of the streak from Crestone, Colorado (see above) and also managed to capture timelapse footage of the entire event. Meanwhile, photographer Jay Shaffer took a striking long-exposure photo of the streak in Taos County, New Mexico (see below).

In some places, the streak appeared alongside auroras that emerged during a G2-class geomagnetic storm, which was triggered earlier in the night when a cloud of charged particles ejected by the sun, known as a coronal mass ejection, slammed into Earth's magnetic field. As a result, many people who witnessed the streak assumed it was the aurora-like phenomenon known as STEVE, which creates long colored ribbons of light in the night sky.

However, what people actually saw was the aftermath of one of China's Zhuque-2E rockets, which launched from the Jiuquan Satellite Launch Center in northwest China at around 12:12 a.m. ET, according to Space News. The rocket released six satellites, each carrying various scientific instruments, before it burned up in Earth's upper atmosphere upon reentry.

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

There was initially some confusion about exactly how the rocket created the stunning light show. "The white streak may have been a de-orbit burn, or perhaps a circularization burn for the deploying satellites," Spaceweather.com representatives wrote.

Others thought it may have been light from the rocket's second stage burning up in our skies, while some people suggested that it may have been an "ionospheric hole," created when rocket fuel reacts with chemicals in the upper atmosphere, triggering streaking aurora-like lights.

However, Jonathan McDowell, an astronomer at the Harvard and Smithsonian Center for Astrophysics who tracks satellite launches and reentries, later revealed on the social platform X that it was caused by a "fuel dump" at an altitude of around 155 miles (250 kilometers) before the rocket de-orbited. The ejected fuel, which trailed behind the rocket, froze into a ribbon of tiny frozen crystals that then reflected sunlight toward Earth's surface, making it shine in the night sky.

Similar light shows often occur when SpaceX's Falcon 9 rockets dump their fuel before re-entering the atmosphere. In these cases, the spacecraft is normally spinning as it dumps the fuel, creating luminous whirlpools of light. Recent examples of these structures, nicknamed SpaceX spirals, include a luminous vortex spotted above the U.K. in March, a "horned" spiral that appeared over mainland Europe in May 2024 and a distant swirl visible from Hawaii in January 2023, among others.

New type of rocket fuel

The Zhuque-2E rocket is a single-use orbital launch vehicle created by Chinese company LandSpace. It stands at around 160 feet (50 meters) tall and can launch up to 13,200 pounds (6,000 kilograms) of payloads into low-Earth orbit (LEO) — the region of space up to 1,200 miles (2,000 km) above Earth's surface, where the majority of Earth-orbiting satellites operate.

Unlike most rockets, which use hydrogen or kerosene-based fuels, Zhuque-2E uses a special hybrid of liquid oxygen and liquid methane, known as "methalox."

In July 2023, the rocket's predecessor, Zhuque-2, became the first methane-fueled rocket to reach LEO, beating the likes of SpaceX, which also uses methalox fuels in its gigantic Starship rocket but is yet to successfully get the spacecraft into a full orbital flight. China has now successfully launched four methane-powered rockets into space.

Methane is a desirable fuel source for rockets because it is easier to store and burns cleaner than hydrogen or kerosene. It can also potentially be produced on other planets, such as Mars, which makes it ideal for solar system exploration.

A newly released video has revealed a gigantic plume of solar wind towering above the sun in a never-before-seen, "cyclone-like" configuration that emerged in the wake of a massive solar explosion. The striking timelapse footage also captured strange lines streaking across the fiery scene like pixelated UFOs — but are actually distant stars.

The video, which was released March 26 by the European Space Agency (ESA), is sped-up footage originally taken over an eight-hour period on Oct. 12, 2022, by ESA's Solar Orbiter. The spacecraft captured the scene by blocking out the main disk of the sun, which enabled the probe's camera to focus on the extremely faint light given off by the flow of superfast charged particles, or solar wind, that streams out of our home star nearly constantly.

This is the first time solar wind has been recorded "flying out from the sun in a twisting, whirling motion," ESA representatives wrote in a statement. "The solar wind particles spiral outwards as if caught in a cyclone that extends millions of kilometres from the sun."

The striking video also shows around a dozen perfectly flat, half-dark, half-light lines that creep across the screen like the UFOs and aliens in arcade games such as "Space Invaders."

These features are actually stars that are moving across the background as the orbiter circles the sun, which show up thanks to an editing technique used to make the video, ESA representatives wrote.

Related: 10 supercharged solar storms that blew us away in 2024

Solar ‘pseudostreamer’

In a new study of the video, released March 26 in The Astrophysical Journal, researchers described the giant solar corkscrew as a "large pseudostreamer" that erupted near the sun's north pole in the wake of a solar flare that launched a cloud of plasma, or coronal mass ejection (CME), into space. The pseudostreamer reached up to 1.5 times as long as the sun is wide and lasted for around three hours.

The "helix" structure of the wind jet is likely the result of Alfvénic fluctuations triggered by waves of ions that oscillate in response to magnetic field disturbances that occurred during the flare, the researchers wrote. They noted that the unique shape may also be tied to the streamer's position near one of the sun's polar regions, where magnetic fields are usually much stronger than near the sun's equator.

The sun is currently experiencing the peak in its roughly 11-year cycle of activity, known as solar maximum, which officially began in early 2024. During this phase, powerful solar flares explode more frequently from the sun and solar wind intensifies. However, this video was captured before solar activity started ramping up, which surprised the scientists.

Until recently, the origin and complex behaviors of solar wind have remained largely elusive. But a new generation of spacecraft is helping to unravel these mysteries.

When the video was recorded, ESA's Solar Orbiter was the only probe capable of capturing solar wind in such great detail. However, ESA's Proba-3 mission, which launched in December 2024, is also capable of viewing solar wind thanks to its ability to create artificial solar eclipses in space. NASA's Parker Solar Probe, meanwhile, was launched in 2018 and has helped to capture important solar wind data during its recent super-close flybys of our home star.

Solar wind is expected to become more extreme over the next few years as we enter the solar "battle zone" — a period after solar maximum when magnetic instabilities on the sun cause large coronal holes to open up on the sun's surface and shoot out extreme solar gusts. These solar events will be much like a dark patch that showered Earth with charged particles last week, triggering significant aurora activity.

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

On Monday (March 24), a giant swirl of light was spotted floating across the night sky in Europe like an ethereal whirlpool. The baffling light show wasn't caused by aliens, as some speculated, but a dying SpaceX rocket preparing to crash back to Earth, shortly after deploying secret cargo into orbit around our planet.

At around 8 p.m. local time (4 p.m. ET), people across the U.K. reported seeing the luminous swirl grow as it slowly streaked across the sky like something from a sci-fi movie, according to the BBC. The light show was most clearly visible above parts of England, including Lincolnshire, Yorkshire, Leicestershire, Suffolk and Essex, as well as in Wales and further afield in Sweden, Croatia, Poland, and Hungary.

Photographer Simon Minnican captured the ethereal scene in a stunning video that showed a bright spot appear and then grow in size before swelling into an ever-expanding vortex. The entire spectacle lasted around 12 minutes, with the spiral of light dissipating roughly 4 minutes after it unfurled.

There was initially some wild speculation about what had caused the unusual light show, with at least one observer blaming UFOs. However, experts quickly pointed out that it was a "SpaceX spiral" — an increasingly common phenomenon triggered by light reflecting off rocket fuel dumped into space by spinning SpaceX rockets before they reenter Earth's atmosphere.

In this case, the spacecraft responsible for the luminous swirl was a Falcon 9 rocket that had launched from the Cape Canaveral Space Force Station in Florida at 1:48 p.m. ET, more than 4,000 miles (6,400 kilometers) from where the bright spiral was later spotted. This rocket was carrying a secret payload for the National Reconnaissance Office, according to Live Science's sister site Space.com.

Related: SpaceX rockets keep tearing blood-red 'atmospheric holes' in the sky, and scientists are concerned

SpaceX spirals occur when the second stage of a Falcon 9 rocket de-orbits and prepares to reenter Earth's atmosphere, where it either burns up or falls into the ocean. During this maneuver, the spacecraft dumps its remaining fuel into space, which then freezes into a cloud of tiny crystals that reflect sunlight to Earth. The second stage is normally spinning when the fuel is released, which is what causes the spiral shape of the resulting cloud — and explains why the vortex continually expands before dissipating.

These spirals were once rare but are becoming more common as the number of Falcon 9 rocket launches increases.

One of the most recent examples was a never-before-seen "horned" spiral reported in May 2024 above parts of Europe. In April 2023, a stunning blue SpaceX spiral photobombed an aurora display above Alaska. The phenomenon has also been spotted twice by a camera attached to the Subaru Telescope on Hawaii's Mauna Kea; first in April 2022 and again in January 2023.

Not every Falcon 9 reentry results in a visible SpaceX spiral. But amateur astronomers can sometimes predict when they are likely to occur based on the rocket's trajectory, payload, spin rate and the time of the launch.

However, in this case, the launch information was not shared in advance because of the secrecy of the mission.

For most of our evolutionary history, human activity has been linked to daylight. Technology has liberated us from these ancient sleep-wake cycles, but there is evidence sunlight has left and continues to leave its mark.

Not only do we still tend to be awake in the daytime and sleep at night, we can thank light for many other aspects of our biology.

Light may have driven our ancestors to walk upright on two legs. Light helps explain the evolution of our skin color, why some of us have curly hair, and even the size of our eyes.

Related: Which animals are evolving fastest?

As we'll explore in future articles in this series, light helps shape our mood, our immune system, how our gut works, and much more. Light can make us sick, tell us why we're sick, then treat us.

Million of years of evolutionary history means humans are still very much creatures of the light.

We stood up, then walked out of Africa

The first modern humans evolved in warm African climates. And reducing exposure to the harsh sunlight is one explanation for why humans began to walk upright on two legs. When we stand up and the Sun is directly overhead, far less sunshine hits our body.

Curly hair may have also protected us from the hot Sun. The idea is that it provides a thicker layer of insulation than straight hair to shield the scalp.

Early Homo sapiens had extra Sun protection in the form of strongly pigmented skin. Sunlight breaks down folate (vitamin B9), accelerates ageing and damages DNA. In our bright ancestral climates, dark skin protected against this. But this dark skin still admitted enough UV light to stimulate vital production of vitamin D.

However, when people colonized temperate zones, with weaker light, they repeatedly evolved lighter skin, via different genes in different populations. This happened rapidly, probably within the past 40,000 years.

With reduced UV radiation nearer the poles, less pigmentation was needed to protect sunlight from breaking down our folate. A lighter complexion also let in more of the scarce light so the body could make vitamin D. But there was one big drawback: less pigmentation meant less protection against Sun damage.

How our skin pigmentation adapted with migration patterns and changing light.

This evolutionary background contributes to Australia having among the highest rates of skin cancer in the world.

Our colonial history means more than 50% of Australians are of Anglo-Celtic descent, with light skin, transplanted into a high-UV environment. Little wonder we're described as "a sunburnt country".

Sunlight has also contributed to variation in human eyes. Humans from high latitudes have less protective pigment in their irises. They also have larger eye sockets (and presumably eyeballs), maybe to admit more precious light.

Again, these features make Australians of European descent especially vulnerable to our harsh light. So it's no surprise Australia has unusually high rates of eye cancers.

We cannot shake our body clock

Our circadian rhythm — the wake-sleep cycle driven by our brains and hormones — is another piece of heavy evolutionary baggage triggered by light.

Humans are adapted to daylight. In bright light, humans can see well and have refined colour vision. But we see poorly in dim light, and we lack senses such as sharp hearing or acute smell, to make up for it.

Our nearest relatives (chimps, gorillas and orangutans) are also active during daylight and sleep at night, reinforcing the view that the earliest humans had similar diurnal behaviors.

This lifestyle likely stretches further back into our evolutionary history, before the great apes, to the very dawn of primates.

The earliest mammals were generally nocturnal, using their small size and the cover of darkness to hide from dinosaurs. However, the meteorite impact that wiped out these fearsome reptiles allowed some mammalian survivors, notably primates, to evolve largely diurnal lifestyles.

If we inherited our daylight activity pattern directly from these early primates, then this rhythm would have been part of our lineage's evolutionary history for nearly 66 million years.

This explains why our 24-hour clock is very difficult to shake; it's so deeply ingrained in our evolutionary history.

Successive improvements in lighting technology have increasingly liberated us from dependence on daylight: fire, candles, oil and gas lamps, and finally electric lighting. So we can theoretically work and play at any time.

However, our cognitive and physical performance deteriorates when our intrinsic daily cycles are disturbed, for instance through sleep deprivation, shift work or jet lag.

Futurists have already considered the circadian rhythms required for life on Mars. Luckily, a day on Mars is around 24.7 hours, so similar to our own. This slight difference should be the least of the worries for the first intrepid martian colonists.

Light is still changing us

In the past 200 years or so, artificial lighting has helped to (partly) decouple us from our ancestral circadian rhythms. But in recent decades, this has come at a cost to our eyesight.

Many genes associated with short-sightedness (myopia) have become more common in just 25 years, a striking example of rapid evolutionary change in the human gene pool.

And if you have some genetic predisposition to myopia, reduced exposure to natural light (and spending more time in artificial light) makes it more likely. These noticeable changes have occurred within many people's lifetimes.

Light will no doubt continue to shape our biology over the coming millennia, but those longer-term effects might be difficult to predict.

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

Exposure to light is crucial for our physical and mental health, as this and future articles in the series will show.

But the timing of that light exposure is also crucial. This tells our body to wake up in the morning, when to poo and the time of day to best focus or be alert. When we're exposed to light also controls our body temperature, blood pressure and even chemical reactions in our body.

But how does our body know when it's time to do all this? And what's light got to do with it?

What is the body clock, actually?

One of the key roles of light is to re-set our body clock, also known as the circadian clock. This works like an internal oscillator, similar to an actual clock, ticking away as you read this article.

But rather than ticking you can hear, the body clock is a network of genes and proteins that regulate each other. This network sends signals to organs via hormones and the nervous system. These complex loops of interactions and communications have a rhythm of about 24 hours.

In fact, we don't have one clock, we have trillions of body clocks throughout the body. The central clock is in the hypothalamus region of the brain, and each cell in every organ has its own. These clocks work in concert to help us adapt to the daily cycle of light and dark, aligning our body's functions with the time of day.

However, our body clock is not precise and works to a rhythm of about 24 hours (24 hours 30 minutes on average). So every morning, the central clock needs to be reset, signalling the start of a new day. This is why light is so important.

Related: Blood test could tell you what time it is in your body

The central clock is directly connected to light-sensing cells in our retinas (the back of the eye). This daily re-setting of the body clock with morning light is essential for ensuring our body works well, in sync with our environment.

In parallel, when we eat food also plays a role in re-setting the body clock, but this time the clock in organs other than the brain, such as the liver, kidneys or the gut.

So it's easy to see how our daily routines are closely linked with our body clocks. And in turn, our body clocks shape how our body works at set times of the day.

What time of day?

Let's take a closer look at sleep

The naturally occurring brain hormone melatonin is linked to our central clock and makes us feel sleepy at certain times of day. When it's light, our body stops making melatonin (its production is inhibited) and we are alert. Closer to bedtime, the hormone is made, then secreted, making us feel drowsy.

Our sleep is also partly controlled by our genes, which are part of our central clock. These genes influence our chronotype — whether we are a "lark" (early riser), "night owl" (late sleeper) or a "dove" (somewhere in between).

But exposure to light at night when we are supposed to be sleeping can have harmful effects. Even dim light from light pollution can impair our heart rate and how we metabolise sugar (glucose), may lead to psychiatric disorders such as depression, anxiety and bipolar disorder, and increases the overall risk of premature death.

The main reason for these harmful effects is that light "at the wrong time" disturbs the body clock, and these effects are more pronounced for "night owls".

This "misaligned" exposure to light is also connected to the detrimental health effects we often see in people who work night shifts, such as an increased risk of cancer, diabetes and heart disease.

How about the gut?

Digestion also follows a circadian rhythm. Muscles in the colon that help move waste are more active during the day and slow down at night.

The most significant increase in colon movement starts at 6.30am. This is one of the reasons why most people feel the urge to poo in the early morning rather than at night.

The gut's day-night rhythm is a direct result of the action of the gut's own clock and the central clock (which synchronizes the gut with the rest of the body). It's also influenced by when we eat.

How about focusing?

Our body clock also helps control our attention and alertness levels by changing how our brain functions at certain times of day. Attention and alertness levels improve in the afternoon and evening but dip during the night and early morning.

Those fluctuations impact performance and can lead to decreased productivity and an increased risk of errors and accidents during the less-alert hours.

So it's important to perform certain tasks that require our attention at certain times of day. That includes driving. In fact, disruption of the circadian clock at the start of daylight savings — when our body hasn't had a chance to adapt to the clocks changing — increases the risk of a car accident, particularly in the morning.

What else does our body clock control?

Our body clock influences many other aspects of our biology, including:

• physical performance by controlling the activity of our muscles
• blood pressure by controlling the system of hormones involved in regulating our blood volume and blood vessels
• body temperature by controlling our metabolism and our level of physical activity
• how our body handles drugs and toxins by controlling enzymes involved in how the liver and kidneys eliminate these substances from the body.

Morning light is important

But what does this all mean for us? Exposure to light, especially in the morning, is crucial for synchronizing our circadian clock and bodily functions.

As well as setting us up for a good night's sleep, increased morning light exposure benefits our mental health and reduces the risk of obesity. So boosting our exposure to morning light — for example, by going for a walk, or having breakfast outside — can directly benefit our mental and metabolic health.

However, there are other aspects about which we have less control, including the genes that control our body clock.

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

Researchers in Birmingham have created the first image of a photon, a lemon-shaped particle of light emitted from the surface of a nanoparticle. The theory that made this image possible, reported Nov. 14 in the journal Physical Review Letters, enables scientists to calculate and understand various properties of these quantum particles — which could open up a range of new possibilities across fields such as quantum computing, photovoltaic devices and artificial photosynthesis.

Light's quantum behavior is well established, with over 100 years of experiments showing it can exist in both wave and particle form. But our fundamental understanding of this quantum nature is much further behind, and we only have a limited grasp of how photons are created and emitted, or of how they change through space and time.

"We want to be able to understand these processes to leverage that quantum side," first author Ben Yuen, a research fellow at the University of Birmingham in the U.K., told Live Science. "How do light and matter really interact at this level?"

However, the very nature of light means the answer to this question has almost limitless possibilities. "We can think of a photon being a fundamental excitation of an electromagnetic field," explained Yuen. These fields are a continuum of different frequencies, each of which could potentially become excited. "You can split up a continuum into smaller parts and between any two points, there's still an infinite number of possible points you could pick," Yuen added.

The result is that the properties of a photon are heavily dependent on the properties of its environment, leading to some incredibly complex math. "At first glance, we would have to write down and solve an infinite number of equations to reach an answer," Yuen said.

Related: High school students who came up with 'impossible' proof of Pythagorean theorem discover 9 more solutions to the problem

To tackle this seemingly impossible task, Yuen and co-author Angela Demetriadou, professor of theoretical nanophotonics at the University of Birmingham, employed a clever math trick to dramatically simplify the equations.

Introducing imaginary numbers — multiples of the impossible square root of -1 — is a powerful tool when handling complex equations. Manipulating these imaginary components allows many of the difficult terms in the equation to cancel each other out. Provided all imaginary numbers are converted back to real numbers before reaching the solution, this leaves a much more manageable calculation.

"We transformed that continuum of real frequencies into a discrete set of complex frequencies," explained Yuen. "By doing that, we simplify the equations from a continuum into a discrete set which we can handle. We can put those into a computer and solve them."

The team used these new calculations to model the properties of a photon emitted from the surface of a nanoparticle, describing the interactions with the emitter and how the photon propagated away from the source. From these results, the team generated the first image of a photon, a lemon-shaped particle never seen before in physics.

Yuen stressed, however, that this is only the shape of a photon generated under these conditions. "The shape changes completely with the environment," he said. "This is really the point of nanophotonics, that by shaping the environment, we can really shape the photon itself."

The team's calculations provide a fundamental insight into the properties of this quantum particle — knowledge that Yuen believes will open up new lines of research for physicists, chemists and biologists alike.

"We could think about optoelectronic devices, photochemistry, light harvesting and photovoltaics, understanding photosynthesis, biosensors, and quantum communication," Yuen said. "And there will be a whole host of unknown applications. By doing this kind of really fundamental theory, you unlock new possibilities in other areas."

From the most distant stars in the sky to the screen in front of your face, light is everywhere. But the exact nature of light, and how it travels, has long puzzled scientists. One question in particular has vexed thinkers from Issac Newton to Albert Einstein: Is light a particle or a wave?

"Whether light is a particle or a wave is a very old question," Riccardo Sapienza, a physicist at Imperial College London, told Live Science. As a species, we seem driven to understand the fundamental nature of the world around us, and this particular puzzle kept 19th-century scientists busy.

Today, there's no doubt about the answer: Light is both a particle and a wave. But how did scientists reach this mind-bending conclusion?

The starting point was to scientifically distinguish between waves and particles. "You would describe an object as a particle if you can identify it as a point in space," Sapienza said. "A wave is an object that you don't define as a point in space and you need to give a frequency of oscillation and distance between maximum and minimum."

The first conclusive evidence of the wave nature of light came in 1801, when Thomas Young performed his now-famous double-slit experiment. He placed a screen with two holes in front of a light source and observed the behavior of the light after it had passed through the slits. The light hitting the wall showed a complicated pattern of bright and dark bands, known as interference fringes.

As the light waves passed through each hole, they generated partial waves that radiated spherically, intercepting each other and adding or subtracting to the final intensity.

"If the light was a particle, you would have ended up with two bunches on the other side of the screen," Sapienza said. "But we have interference, and we see light everywhere after the screen, not just at the position of the holes. That's proof that light is indeed a wave."

Eighty-six years later, Heinrich Hertz became the first to demonstrate the particle nature of light. He noticed that when ultraviolet light shone on a metal surface, it generated a charge — a phenomenon called the photoelectric effect. However, the significance of his observation wasn't fully understood until many years later.

Related: What is the speed of light?

Atoms contain electrons in fixed energy levels. Shining light on them is therefore expected to give the electrons energy and enable them to escape from the atom, with brighter light liberating electrons faster. But in experiments following Hertz's work, several unusual observations seemed to completely contradict this classical understanding of physics.

It was Einstein who finally solved this puzzle, for which he was awarded a Nobel prize in 1921. Rather than absorbing light continuously from a wave, atoms actually receive energy in packets of light called photons, explaining odd observations such as the existence of a cutoff frequency.

But what determines whether light behaves as a wave or as a particle? According to Sapienza, this isn't the right question to be asking. "Light is not sometimes a particle and sometimes a wave," he said. "It is always both a wave and a particle. It's just that we highlight one of the properties depending on which experiment we do."

In day-to-day life, we mostly experience light as a wave, and it's this form that physicists find most useful to manipulate.

"There's a full field called metamaterials — by shaping a material with the same features as light, we can enhance the interaction of light with the material and control the waves,” Sapienza said. "For example, we can make solar absorbers that can absorb light more efficiently for energy generation or metamaterial MRI probes which are much more effective."

However, light's double nature, known as wave particle duality, is absolutely fundamental to the existence of the world as we know it. This strange twinned behavior also extends to other quantum particles, like electrons.

"You could not have an atom be stable if you didn't have quantum mechanics with the electrons in specific states," Sapienza said. "If you remove the fact that it is a particle, you remove the fact that it has a specific energy and life could not exist."

Virginia's "rainbow swamp" is a flooded forest whose waters take on a magical, multicolored sheen in the winter months. Under certain lighting conditions, the swamp turns into a giant, luminous rainbow broken up by the shadows of bald cypress trees (Taxodium distichum) and cypress knees — cone-shaped humps that grow vertically above the trees' roots.

The rainbow swamp is one of many along the Bald Cypress Trail at First Landing State Park, which is located where English colonists first landed in 1607, according to the park's website. Most days of the year, the swamp looks like any other forested wetland — rather murky and opaque. But occasionally, in late fall and winter, the stagnant pool puts on a dazzling light show.

Related: Extremely rare 'rainbow clouds' light up Arctic skies for 3 days in a row

The rainbow effect results from leaf decay in the swamp during fall and winter, according to a Facebook post from March 2024. "The trees drop their needlelike leaves in the fall that decompose in the swamp and the resulting matter, when hit at just the right angle by sunlight, gives off this prismatic appearance," park representatives wrote in the post.

Bald cypress leaves contain natural oils that ooze into the swamp as the leaves break down. The oils then separate from the water and form a film on the surface that reflects light much like a puddle of gasoline would. Biological processes in the soil, resulting from bacteria breaking down iron, can also contribute to the rainbow effect, Jeff Ripple, a former Florida swamp walk leader, told the BBC in 2018.

The longer the swamp goes undisturbed, the stronger the effect grows. "Movement by sheet flow, current or wind disturbance would destroy the fragile rainbow film," Ripple said, adding that the effect is usually visible in smaller pools of water.

Rainbow swamps occur throughout southern US states, overlapping with the range of bald cypress trees. Tallahassee, Florida, for example, is home to a flooded forest that lights up like a disco ball around mid-February. "I have seen this occur about 10 times in the 40 years I have lived here," Michael Hussey, a retired engineer who owns the land the swamp sits on, told the BBC. "It's beautiful to see."

Discover more incredible places, where we highlight the fantastic history and science behind some of the most dramatic landscapes on Earth.

NASA's New Horizons spacecraft has made the most precise and direct measurements of the total amount of light produced by our universe.

The question of just how dark the universe is has vexed astronomers for decades, because from our stretch of the solar system, scattered sunlight and interplanetary dust and ice interfere with the measurement of the ambient light produced by the cosmos' hundreds of billions of galaxies.

Now, more than 18 years after its launch and nine years after mapping the surface of Pluto, the New Horizons spacecraft has produced an answer. Drifting more than 5.4 billion miles (8.8 billion kilometers) from Earth in the cold, dark space of the outer solar system, the spacecraft measured the universe's light. The researchers published their findings Wednesday (Aug. 28) in the The Astrophysical Journal.

The background of visible light added up over the universe's lifespan (called the cosmic optical background or COB) is important to astronomers because it helps them to match the light coming from stars and the exteriors of black holes with that predicted by theory. 

Related: Supercharged 'cocoon of energy' may power the brightest supernovas in the universe

If these two figures line up, then our current picture of the universe is mostly correct; but if they misalign, it could mean that there's more going on in the universe than we presently know. Yet accurately measuring the COB from Earth, or even the inner solar system, is extremely difficult.

"People have tried over and over to measure it directly, but in our part of the solar system, there's just too much sunlight and reflected interplanetary dust that scatters the light around into a hazy fog that obscures the faint light from the distant universe," co-author Tod Lauer, a New Horizons co-investigator and an astronomer at the National Science Foundation NOIRLab in Tucson, Arizona, said in the statement. "All attempts to measure the strength of the COB from the inner solar system suffer from large uncertainties."

To overcome this problem, the New Horizons spacecraft waited until it was far away in the Kuiper Belt, on its way to interstellar space. Then, it used its body to shield the Long Range Reconnaissance Imager (LORRI) from the sun's light and pointed itself away from the Milky Way's bright core. The spacecraft then snapped two-dozen snapshots of the universe.

After carefully calibrating the light levels observed with those taken in infrared by the Planck satellite to screen out dust, the researchers arrived at their estimate for the universe's visible light — a radiant intensity 11.16 nanowatts per steradian.

The result was consistent with the light intensity thought to be generated by all galaxies over the past 12.6 billion years, meaning that (at least in the visible spectrum) astronomers are unlikely to be missing anything big in their models.

"The simplest interpretation is that the COB is completely due to galaxies," Lauer said. "Looking outside the galaxies, we find darkness there and nothing more."

New research suggests that extreme objects known as "kugelblitze" — black holes formed solely from light — are impossible in our universe, challenging Einstein's theory of general relativity. The discovery places significant constraints on cosmological models and demonstrates how quantum mechanics and general relativity can be reconciled to address complex scientific questions.

Black holes — massive objects with such a strong gravitational pull that not even light can escape their grasp — are among the most intriguing and bizarre objects in the universe. Typically, they form from the collapse of massive stars at the ends of their life cycles, when the pressure from thermonuclear reactions in their cores can no longer counteract the force of gravity.

However, more exotic hypotheses exist regarding black hole formation. One such theory involves the creation of a "kugelblitz," German for "ball lightning." (The plural form is "kugelblitze.")

"A kugelblitz is a hypothetical black hole that, instead of forming from the collapse of 'ordinary matter' (whose main constituents are protons, neutrons, and electrons), is formed from concentrating humongous amounts of electromagnetic radiation, such as light," study co-author José Polo-Gómez, a physicist at the University of Waterloo and the Perimeter Institute for Theoretical Physics in Canada, told Live Science in an email.

"Even though light does not have mass, it does carry energy," Polo-Gómez said,  adding that, in Einstein's theory of general relativity, energy is responsible for creating curvatures in space-time that result in gravitational attractions. "Because of that, it is in principle possible for light to form black holes — if we concentrate enough of it in a small enough volume," he said.

Related: Tweak to Schrödinger's cat equation could unite Einstein's relativity and quantum mechanics, study hints

These principles hold true under classical general relativity, which does not account for quantum phenomena. To explore the potential impact of quantum effects on kugelblitz formation, Polo-Gómez and his colleagues examined the influence of the Schwinger effect.

"When there is an incredibly intense electromagnetic energy — for example, due to huge concentrations of light — part of this energy transforms into matter in the form of electron-positron pairs," lead study author Álvaro Álvarez-Domínguez of the Institute of Particle and Cosmos Physics (IPARCOS) at the Universidad Complutense de Madrid, told Live Science in an email. "This is a quantum effect called the Schwinger effect. It is also known as vacuum polarization."

In their study, which has been accepted for publication in the journal Physical Review Letters but has not been published yet, the team calculated the rate at which electron-positron pairs produced in an electromagnetic field would deplete energy. If this rate surpasses the replenishment rate of the electromagnetic field's energy in a given region, a kugelblitz cannot form.

The team found that, even under the most extreme circumstances, pure light could never reach the required energy threshold to form a black hole.

"What we prove is that kugelblitze are impossible to form by concentrating light, either artificially in the laboratory or in naturally occurring astrophysical scenarios," study co-author Luis J. Garay, also of IPARCOS, told Live Science. "For instance, even if we used the most intense lasers on Earth, we would still be more than 50 orders of magnitude away from the intensity required to create a kugelblitz."

This finding has profound theoretical implications, significantly constraining previously considered astrophysical and cosmological models that assume the existence of kugelblitze. It also dashes any hopes of experimentally studying black holes in laboratory settings by creating them through electromagnetic radiation.

Nonetheless, the study's positive outcome shows that quantum effects can be efficiently integrated into problems involving gravity, thus providing clear answers to actual scientific questions.

"From a theoretical viewpoint, this work showcases how quantum effects can play an important role in the understanding of the formation mechanisms and appearance of astrophysical objects," Polo-Gómez said.

Inspired by their findings, the researchers plan to continue exploring the influence of quantum effects on various gravitational phenomena, which have both practical and fundamental significance.

"Several of us are very interested in continuing the study of the gravitational properties of quantum matter, particularly in scenarios where this quantum matter violates traditional energy conditions," said Eduardo Martín-Martínez, also of the University of Waterloo and the Perimeter Institute. "This type of quantum matter can, in principle, give rise to exotic space-times, resulting in effects such as repulsive gravity or producing exotic solutions like the Alcubierre warp drive or traversable wormholes."

If you've ever gotten dressed in the dark and later realized that the shirt you were wearing was not the color you thought it was, you're not alone. Identifying colors can be challenging in the dark, and even in low light, different colors can look remarkably similar. 

But why is it harder to discern colors in the dark than it is in bright light?

Humans' ability to perceive color varies due to how we see under different lighting conditions. Human eyes contain two types of photoreceptors, or nerve cells that detect light: rods and cones. Each photoreceptor contains light-absorbing molecules, called photopigments, that undergo a chemical change when struck by light. This triggers a chain of events in the photoreceptor, prompting it to send signals to the brain.

Rods are responsible for enabling vision in the dark, known as scotopic vision. They're made of layers and layers of photopigments, said Sara Patterson, a neuroscientist at the University of Rochester in New York. 

Related: The 5 human senses — and a few more you might not know about 

Rods are particularly good at picking up light even when it's dark because "every single one of those stacks is a chance for photons to get absorbed," she said. Photons are particles of electromagnetic radiation — in this case, visible light — and rods can be activated by exposure to relatively few photons.

Cones, on the other hand, are responsible for vision in bright light, or photopic vision. Most people have three types of cone cells, each of which is sensitive to a different range of wavelengths of visible light, which correspond to different colors. Small changes in the light-absorbing molecules in different cones make them specialized in detecting red, green or blue light.

But importantly, individual cone cells can't distinguish between colors, said A. P. Sampath, a neuroscientist at UCLA. When a molecule inside the cone cell absorbs a photon, it only activates the cone; at that point, no information about the light's color or intensity has been processed. Color vision arises when the brain combines the responses from all three types of cones in the eyes — tiny biological circuits transform those responses into the colors we see.

Cones dominate vision in bright light because rods quickly become saturated, or overwhelmed with photons, and the brain essentially tunes out the rods' activity. That's why we can see colors easily in bright light. But as it gets darker, as the sun sets or you switch off the lights in a room, rods start to take over because they're more sensitive to light than cones are. 

The rods dominate night vision, while cones are only weakly activated. Unlike cones, though, rods come in only one type. Color vision comes from comparing the responses of the three types of cone cells, which isn't possible in rod-dominated vision. So, in the dark, we can't distinguish colors well.

However, rods might still influence color perception under certain conditions. In dim light, our eyes operate in an intermediate range known as mesopic vision, in which both rods and cones contribute to vision but neither dominates. 

"In this mesopic range, there's reason to believe that rods may contribute to color processing as well, by providing a distinct spectral sensitivity to compare against the cones," Sampath said. Rods are most sensitive to green light, and in this intermediate range, they provide extra information to the brain to compare against that from the cone cells.

This crossover between rod vision and cone vision also produces the Purkinje effect, in which red hues look dark or bluish under dim light and purple, blue and green suddenly pop, Patterson said. The Purkinje effect is particularly noticeable at twilight or during a total solar eclipse.

Even though we can't see color well at night, our visual system lets us take in information over an enormous range of light intensities, from a moonless night to blindingly bright ski slopes, Sampath said. 

"One of the things that's amazing about the visual system is that we have this enormous range of intensities and it's shifting continuously," he said. "And yet we can accommodate 12 orders of magnitude of light intensity. There's no synthetic detectors that can manage this type of performance."

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

A bizarre, "horned" spiral of light recently photobombed a vibrant aurora display above Europe. The misshaped luminous swirl was painted in the sky by a dying SpaceX rocket, but it is unlike any light show we have seen before. 

The stunning galaxy-like spiral appeared above parts of Poland, Lithuania and the Czech Republic on May 2 at around 9:00 p.m. GMT (4:00 p.m. EDT), Spaceweather.com reported. Around 90 minutes earlier, a SpaceX Falcon 9 rocket carrying a pair of Earth-observation satellites launched from the Vandenberg Space Force Base in California.

The swirling light show is an example of what researchers commonly call "SpaceX spirals," which are made up of fuel dumped in space by Falcon 9 rockets shortly before they fall back to Earth and burn up in the atmosphere. The fuel freezes into tiny crystals that reflect sunlight and form the shape of a spiral because the rockets spin as they discard it.

Normally, these spirals have a perfect vortex shape. But photos of the recent spiral above Europe show this spiral had two faint, horn-like pillars of light, which have not been seen in any previous spirals. It is not clear what caused the horns to form, but it is likely tied to how the rocket dumped its fuel, Spaceweather.com reported.

The light show only lasted for around 10 minutes before disappearing completely as the frozen fuel began to disperse.

Related: Controversial paper claims satellite 'megaconstellations' like SpaceX's could weaken Earth's magnetic field and cause 'atmospheric stripping.' Should we be worried?

This spiral coincided with a strong G3 geomagnetic storm that began on May 2 after a coronal mass ejection from the sun smashed into Earth's magnetic field, according to the National Oceanic and Atmospheric Administration (NOAA). As a result, the northern lights can also be seen in some of the images. One photographer even captured a timelapse video of the spiral as the aurora danced in the sky.

SpaceX spirals are becoming more common in the night sky as the company has increased the number of launches over the last few years. 

Recently, a massive white SpaceX spiral photobombed the northern lights above Iceland in March. Similarly, stunning swirls were also spotted above Alaska in April 2023 and over Hawaii in April 2022. 

But SpaceX spirals aren't the only atmospheric light shows caused by the company's Falcon 9 rockets. 

As the dying spacecraft reenter the atmosphere, they release chemicals that can react with ionized oxygen in the upper atmosphere, causing the molecules to recombine into normal atoms and temporarily emit bright red light like an aurora. Scientists call this an "atmospheric hole," and such holes are also becoming more common as the rate of SpaceX launches rises.

In March, a photographer managed to capture a timelapse photo of a Falcon 9 rocket's reentry burn, which created a strange dashed line in the sky.

The future of cellular data transfer could lie in "curving" light beams midair to deliver 6G wireless networks with blazing-fast speeds — bypassing the need for line of sight between transmitter and receivers. 

In a new study published March 30 in the journal Nature's Communications Engineering, researchers explained how they developed a transmitter that can dynamically adjust the waves needed to support future 6G signals. 

The most advanced cellular communications standard is 5G. Expected to be thousands of times faster, 6G will begin rolling out in 2030, according to the trade body GSMA. Unlike 5G, which mostly operates in bands under 6 gigahertz (GHz) in the electromagnetic spectrum, 6G is expected to operate in sub-terahertz (THz) between 100 GHz and 300 GHz, and THz bands — just below infrared. The closer this radiation is to visible light, the more prone the signals are to be blocked by physical objects. A major challenge with high-frequency 5G and future 6G is that signals need a direct line of sight between a transmitter and receiver. 

But in the experiments, the scientists showed that you can effectively "curve" high-frequency signals around obstacles such as buildings.

"This is the world's first curved data link, a critical milestone in realizing the 6G vision of high data rate and high reliability," said Edward Knightly, co-author of the study and professor of electrical and computer engineering at Rice University, in a statement.

Related: Scientists create light-based semiconductor chip that will pave the way for 6G

The photons, or light particles, that make up the THz radiation in this region of the electromagnetic spectrum generally travel in straight lines unless space and time are warped by massive gravitational forces — the kind that black holes exert. But the researchers found that self-accelerating beams of light — first demonstrated in research from 2007 — form special configurations of electromagnetic waves that can bend or curve to one side as they move through space. 

By designing transmitters with patterns that manipulate the strength, intensity and timing of the data-carrying signals, the researchers made waves that worked together to create a signal that remained intact even if its route to a receiver was partially blocked. They found that a light beam can be formed that adjusts to any objects in its way by shuffling data to an unblocked pattern. So while the photons still travel in a straight line, the THz signal effectively bends around an object.

Bending toward a 6G future

While bending light without the power of a black hole isn't new research, what's significant about this study is it could make 6G networks a practical reality. 

5G millimeter wave (mmWave) currently offers the fastest network bandwidth by occupying the higher 5G radio frequencies between 24GHz and 100GHz of the electromagnetic spectrum to deliver theoretical maximum download speeds of 10 to 50 gigabits (billions of bits) per second. THz rays sit above mmWave in a frequency between 100 GHz and 10,000 GHz (10 THz), which is needed to deliver data transfer speeds of one terabit per second — nearly 5,000 times faster than average U.S. 5G speeds. 

"We want more data per second," Daniel Mittleman, a professor at Brown's School of Engineering, said in a statement. "If you want to do that, you need more bandwidth, and that bandwidth simply doesn't exist using conventional frequency bands."

But due to the high frequencies they operate in, both 5G mmWave and future 6G signals need a direct line of sight between a transmitter and receiver. But by practically delivering a signal over a curved trajectory, future 6G networks wouldn't need buildings to be covered in receivers and transmitters.

However, a receiver needs to be within the near-field range of the transmitter for signal bending to work. When using high-frequency THz rays, this means some 33 feet (10 meters) apart, which is no good for city-wide 6G but could be practical for next-generation Wi-Fi networks.

"One of the key questions that everybody asks us is how much can you curve and how far away," Mittleman said. "We've done rough estimations of these things, but we haven't really quantified it yet, so we hope to map it out."

While curving THz signals holds a lot of promise for future 6G networks, the use of THz spectrum is still in its infancy. With this study, the scientists said we have gotten a step closer to realizing cellular wireless networks with unparalleled speeds.

More than 1,000 never-before-seen space rocks have been discovered in the solar system after secretly photobombing images of the cosmos for decades. A combination of artificial intelligence and citizen scientists helped uncover the asteroids hiding in archival photos from the Hubble Space Telescope, a new study shows. 

Our cosmic neighborhood is littered with asteroids. Scientists have already discovered more than 1.3 million of the space rocks, most of which lie in the asteroid belt between Mars and Jupiter, according to NASA. There are likely hundreds of thousands if not millions more asteroids waiting to be discovered. However, these remaining space rocks are likely the smallest and therefore faintest bodies in the solar system, which makes them very hard to spot.     

In the new study, published March 15 in the journal Astronomy and Astrophysics, researchers highlighted 1,031 previously uncategorized asteroids from archival Hubble data. They were identified by artificial intelligence (AI) that was trained by thousands of citizen scientists to spot faint streaks of light left behind by the tiny space rocks.

"We were surprised to see such a large number of candidate objects," study lead author Pablo García-Martín, a researcher at the Autonomous University of Madrid in Spain, said in a statement. 

Although these asteroids were discovered randomly, their projected orbits suggest that most of them belong to a single population within the asteroid belt, which makes them even more valuable to researchers. 

"There was some hint that this population existed, but now we are confirming it," García-Martín said. "This is important for providing insights into the evolutionary models of our solar system."

Related: 'Planet killer' asteroids are hiding in the sun's glare. Can we stop them in time?

The asteroid streaks in the Hubble photos are the result of the space telescope racing around Earth as it takes long-exposure images of distant galaxies. The asteroids would normally go unnoticed in images like this because the space rocks are millions of times fainter than the faintest stars in the night sky. However, the streaks make them much more noticeable and enable astronomers to infer information on their size and orbital characteristics.

Since 2019, more than 11,000 citizen scientists have been combing through images in search of these streaks. This project, known as Hubble Asteroid Hunter (HAH), has massively helped astronomers who would otherwise have had to sift through the images themselves.  

In the new study, researchers gave HAH members a group of Hubble images to sort through and then used the results as a training set for an AI to help it learn how to detect the photobombing space rocks. The team then used this AI to comb through 37,000 Hubble images taken over a 19-year period in search of new asteroids. The AI identified a total of 1,701 candidates, of which 1,031 had never been seen before. 

The researchers were surprised by how well the AI identified the asteroids and are now hoping to use similar methods to search through different kinds of archival datasets to pull out other hidden gems from these astronomical treasure troves.

Scientists have discovered a new mechanism in which a concentrated laser beam can change the magnetic state of a solid material. The finding could one day be harnessed in ultrafast computing memory, the researchers say.

The scientists formulated a new equation that describes the link between the amplitude of the magnetic field of light, its frequency and the energy absorption properties of a magnetic material. The scientists published their findings in a study on Jan. 3 in the journal Physical Review Research.

The equation is "completely new and also very elemental," study co-author Amir Capua, a physics professor at Hebrew University of Jerusalem, told Live Science.

Although the discovery builds on the field known as "magneto-optics," this represents a new paradigm because scientists didn't previously understand that the magnetic component of a rapidly oscillating light wave can control magnets, he said. The equation describes the characteristics of this interaction.

Computer memory uses miniature electromagnets that are magnetized with voltage to enable the binary states of "on" or "off" to encode data, which are read and reinterpreted by a processor as 1 or 0. 

The most common computing memory, like those found in laptops or phones, comes in the form of dynamic random access memory (DRAM). This is volatile, meaning when power is switched off, all data held is lost, but it's easier to engineer, uses common materials and has low error rates — and those few errors are easy to detect and fix.

The new finding is more relevant for a technology called magnetoresistive random access memory (MRAM), which is a non-volatile memory more commonly used in spacecraft as well as military and other industrial applications, according to MRAM-info.

Related: 'Universal memory' breakthrough brings the next generation of computers 1 step closer to major speed boost

Interaction between a magnetic material and radiation is well established when they are in equilibrium, but less is known about this relationship when they are not in equilibrium. It's also an area that overlaps with the weird laws of quantum mechanics, which are being harnessed to build quantum computers.

"We've arrived at a very elementary equation describing this interaction. It lets us completely reconsider optical magnetic recording and navigate our way to a dense, energy-efficient, cost-efficient optical magnetic storage device that doesn't even exist yet," Capua said.

Previous efforts to use the magnetic component of a light beam to flip a magnetic bit in this way were not effective, Capua said. But the new equation could help researchers to successfully incorporate the mechanism, he said.

In the far future, this technology could lead to MRAM components that are faster and more efficient than today's state-of-the-art RAM units, he added.

Optical cycle times (the time for an optical electromagnetic wave to complete an oscillation, in megahertz) in the technology could be a million times faster than in conventional memory. Electrical cycle times operate on nanoscale timescales (a second is 1 billion nanoseconds) whereas typical optical beams work in picoseconds (a second is 1 trillion seconds). 

It may also one day lead to quantum memory for quantum computers, in which a beam of light can fix a magnetic bit in neither 0 nor 1 but a superposition of the two states — much like how qubits work in quantum computers. Even though that's beyond the precision engineering of today, Capua said his team's findings could lead to the discovery of materials that could one day be used in such technology.

It can also make digitized memory systems more energy-efficient by giving the device more control over the strength and duration of the light beam and its effects. "The duration of the optical beam and its energy can be chosen to reduce the writing power. Obviously, when the device is idle it doesn't consume any energy since magnetic memories are nonvolatile," he said.

Astronomers think they've detected an extremely rare, luminous phenomenon known as a "glory" in the hellish atmosphere of a distant exoplanet. If the finding is confirmed, it would be the first time one of these rainbow-colored light shows has been spotted outside the solar system.

The exoplanet, WASP-76 b, is located around 637 light-years from Earth. It was first discovered in 2013 by the Wide Angle Search for Planets (WASP) project, which looks for planets as they pass between, or transit, their parent star and Earth.

The exoplanet — which may have cannibalized a smaller, Mercury-size neighbor in the past — is around 90% the mass of Jupiter but about twice as wide. It is unusually close to its home star, orbiting around 20 times closer than Mercury orbits the sun. As a result, it takes WASP-76 b just 1.8 days to complete one trip around its star.

In 2020, researchers discovered that the planet is tidally locked, meaning one side is always facing its home star, just as the moon faces Earth. As a result, the exoplanet's sunlit side is around 4,350 degrees Fahrenheit (2,400 degrees Celsius), while its dark side is slightly cooler. Researchers think that, due to this subtle temperature difference, metals like iron could be vaporized on the light side and then condense into rain on the dark side.

In a new study, published April 5 in the journal Astronomy & Astrophysics, researchers examined new data on WASP-76 b collected by multiple spacecraft, including the European Space Agency's (ESA) Characterising Exoplanet Satellite and NASA's Transiting Exoplanet Survey Satellite. This analysis revealed a "bright spot" of light coming from the exoplanet's eastern limb, along the boundary where the planet's permanent day and night meet.

The researchers think this bright spot could be a "glory." This rare visual phenomenon, when seen on Earth, is normally made up of concentric rainbow rings forming a giant circle.

Related: 10 extreme exoplanets that are out of this world

On Earth, glories are formed when sunlight squeezes through small holes between water molecules in clouds or fog, bending the light and separating it into its individual wavelengths. This is similar to how rainbows work, except with glories, the light is bent by diffraction, which is when light is bent around an obstruction, instead of refraction, or when light is bent as it passes through different mediums.

"It requires very peculiar conditions," study lead author Olivier Demangeon, an astronomer at Portugal's Institute of Astrophysics and Space Sciences, said in a statement. "First, you need atmospheric particles that are close-to-perfectly spherical, completely uniform and stable enough to be observed over a long time." The observer also has to be at just the right orientation to be able to see the diffracted light, he added.

However, it is possible that, if given similar conditions, the effect might happen on other planets. We have already seen this phenomenon elsewhere in the solar system, on Venus, according to ESA.

Researchers are unsure exactly how a glory would form on WASP-76 b. But given that the bright spot has been visible across multiple years, the medium that diffracts the light is likely a lot more stable than the water vapor in our planet's atmosphere.

However, the glory theory is based on an "incredibly faint signal," so it's not certain, Matthew Standing, an exoplanet scientist at ESA who was not involved in the study, said in the statement.

"Further proof is needed to say conclusively that this intriguing 'extra light' is a rare glory," Theresa Lüftinger, an ESA astrophysicist who was not involved in the study, said in the statement. We will likely need more powerful instruments, like those on the James Webb Space Telescope, to get this proof, she added.

If it is a glory, researchers could use the data to hunt for more extrasolar examples of these light shows in the atmospheres of other exoplanets to learn more about this puzzling phenomenon.

Striking new photos show a perfect dashed line of light left behind by a dying SpaceX rocket in the night sky above Arizona. The luminous streak, which is the result of some clever photo trickery, is the latest reminder of the company's rapidly increasing launch schedule. 

On Saturday (March 30th), SpaceX launched two of their Falcon 9 rockets in less than four hours, Live Science's sister site Space.com reported. The first rocket, which was carrying the Eutelsat 36D telecommunications satellite, took off at 5:52 p.m. EDT from NASA's Kennedy Space Center (KSC) in Florida. The second rocket, which was carrying 23 of the company's Starlink satellites, launched from the Cape Canaveral Space Force Center, located next door to KSC, at 9:30 p.m. EDT.

After deploying their payloads, the rockets' second stages — the main part of the rocket that separates from the rocket's reusable boosters — underwent controlled deorbit burns, which caused them to fall toward Earth and burn up in the planet's upper atmosphere.

Photographer Jeremy Perez had initially planned to capture the deorbit burn of the first rocket from near his home in Flagstaff, AZ but was left empty-handed due to thick cloud coverage. But by the time the second rocket began the same maneuver, the skies had cleared and Perez was able to catch some stunning images of the deorbiting debris, Spaceweather.com reported. 

In the new images, Perez combined multiple long-exposure shots of the ignited second stage as it passed overhead. The breaks in the luminous streak represent points where the camera's shutter was closed. 

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

In real-time the event appeared very differently: "It looked like a delicate, cometary dandelion poof drifting overhead," Perez told Spaceweather.com. The light also appeared white in real-time instead of the bright blues seen in the photos, he added.

In zoomed-in versions of the photos, you can also see a second dimmer line alongside the falling space junk. This streak is made up of light from the satellites deployed by the rocket, which were drifting alongside it before it started its final maneuver.

An increasingly common sight 

Saturday's twin launches were not the only SpaceX launches this week. 

On Monday (April 1), another Falcon 9 lifted off from the Vandenburg Space Force base in California and later deployed 22 more Starlink satellites into orbit, Space.com reported. The company also plans to launch two more Falcon 9 rockets on Friday (April 5) and Sunday (April 7), which will both deploy more satellites into orbit, according to SpaceFlightNow.com.  

The continued increase in SpaceX launches greatly enhances the chances of people seeing deorbiting material or other phenomena caused by the dying rockets, such as SpaceX spirals — swirls of light created by frozen rocket fuel ejected from deorbiting Falcon 9 boosters. For example, on March 4, one of these spirals briefly outshone the northern lights across large parts of the Arctic. 

Falcon 9 rockets can also be seen for miles as they rise into space and can occasionally punch holes in the upper atmosphere, triggering blood-red aurora-like light shows. 

But these light shows are not the only aspect of these ever-increasing launches that are catching people's eyes. Experts are also concerned with the number of Starlink satellites that are being deployed into low-Earth orbit, which are obscuring our ability to study the cosmos.

When these newly-launched satellites inevitably fail and are sent to burn up in the upper atmosphere, they will also release high levels of metal pollution in our skies, which could have potentially damaging impacts. 

What was little more than a speck of light for the Hubble Space Telescope has been revealed as one of the oldest galaxies ever discovered — and the finding owes itself to none other than Hubble's younger sibling: The James Webb Space Telescope.

The James Webb Space Telescope international "Glass" Collaboration made detailed observations of the galaxy, dubbed Gz9p3, which is seen as it was just 510 million years after the Big Bang. That's during the relative infancy of the universe, which is now 13.8 billion years old.

The team discovered that, much like other early galaxies seen by the JWST, Gz9p3 is far more massive and mature than expected for a galaxy in the infant universe. During the ancient time period in which it's been spotted, it already appears to contain several billion stars.

When it comes to the cosmic conundrum of how early galaxies grew to become so massive so quickly Gz9p3 could be a real puzzle. Not only is it more massive than expected, but it is around 10 times more massive than other galaxies the JWST has seen in similar eras of the universe's history.

Related: James Webb telescope discovers the oldest, most distant black hole in the universe

"Just a couple of years ago, Gz9p3 appeared as a single point of light through the Hubble Space Telescope," Kit Boyett, team member and a scientist at the University of Melbourne, wrote for the institute's Pursuit publication. "But by using the JWST we could observe this object as it was 510 million years after the Big Bang, around 13 billion years ago."

Gz9p3 is simply remarkable. Besides its size and maturity, its shape also reveals clues to its creation.

Was Gz9p3 created by an early galaxy merger?

Using the JWST and direct imaging, the team was able to determine that Gz9p3 has a complex shape with two bright patches that reveal its two dense nuclei. That indicates Gz9p3 was likely created when two early galaxies smashed together in the infant universe. This collision may have still been ongoing during the time at which astronomers noticed Gz9p3 with the JWST.

"The JWST imaging of the galaxy shows a morphology typically associated with two interacting galaxies. And the merger hasn't finished because we still see two components," Boyett explained. "When two massive objects join like this, they effectively throw away some of the matter in the process. So, this discarded matter suggests what we observed is one of the most distant mergers ever seen."

In addition to determining the age, mass and shape of this ancient galaxy, Boyett and colleagues were able to probe deeper within Gz9p3 to examine the stellar population of these colliding galaxies. Because young stars are brighter than their older counterparts, they usually dominate galaxy images, especially those that are so distant their light has been traveling to Earth for billions of years.

"For example, a young bright population sparked by the galaxy merger, less than a few million years old, outshines an older population already over 100 million years old," Boyett continued.

The Glass collaboration worked around this by taking spectroscopic observations of Gz9p3 as well as by tapping into direct imaging.  Spectroscopy can be used to determine the elements that make up stars; because young and old stars have different compositions, this allowed the researchers to separate the two categories in this early galaxy.

Older stars have worked their way through the hydrogen supply in their cores, having already fused it all into helium and then fusing this helium to create even heavier elements, which astronomers call "metals." This means older stars are richer in metals than younger stars, which are still dominated by hydrogen and some helium.

The study team used the JWST to detect specific elements in the older star population of Gz9p3. These target elements included silicon, carbon and iron, the latter of which is the heaviest element that can be synthesized by stars. This means these stars, when they died in supernova explosions, would have enriched the early universe with metals. Much of this metal content would have gone on to become the building blocks of the next generation of stars.

In addition, the team discovered that the population of old stars in Gz9p3 was much larger than previously suspected. This means that, while astronomers have been aware of this cycle of stellar life and death and the increasing metal enrichment of subsequent generations of stars, the Gz9p3 observations indicate galaxies may have become "chemically mature" faster than had been suspected previously.

"These observations provide evidence of a rapid, efficient build-up of stars and metals in the immediate aftermath of the Big Bang, tied to ongoing galaxy mergers, demonstrating that massive galaxies with several billion stars existed earlier than expected," Boyett wrote.

A history of violence

Galaxies that sit isolated from their galactic counterparts do form stars, but the process is slow and ends when that galaxy exhausts its reservoir of gas and dust, the materials that form stars.

For galaxies close to each other, the process of star formation can be sped up and even revived after it has drawn to a halt. That's because when these galaxies are drawn together by a mutual gravitational attraction, they collide. The merger then causes an inflow of fresh gas that kickstarts a period of rapid star birth called a "starburst," meaning mergers provide an excellent way for galaxies to rapidly grow their stellar populations.

Most large galaxies in the universe have grown this way; our own galaxy, the Milky Way, shows a history of mergers itself. For instance, it has been involved in the cannibalization of smaller satellite galaxies that once orbited it. The Milky Way currently forms stars at a stunted rate, but this will change when it collides with our neighboring galaxy, Andromeda, in around 4.5 billion years. This will cause an influx of gas that kicks off a fresh bout of starburst.

Thanks to observations of Gz9p3, astronomers are getting the message that this channel for rapid mass accumulation and star birth was a bigger factor in the early universe than predicted.

"These observations of Gz9p3 show that galaxies were able to accumulate mass quickly in the early universe through mergers, with star formation efficiencies higher than we expected," Boyett explained. "This and other observations using the JWST are causing astrophysicists to adjust their modeling of the early years of the universe.

"Our cosmology isn't necessarily wrong, but our understanding of how quickly galaxies formed probably is, because they are more massive than we ever believed could be possible."

The team's research was published on March 7 in the journal Nature Astronomy.

Originally posted on Space.com.

A massive swirl of bright white light seemingly appeared from out of nowhere in the night sky above the Arctic last week, briefly upstaging a vibrant aurora display that spanned thousands of miles.

The ethereal, galaxy-shaped light show was caused by an illuminated cloud of frozen fuel that was dumped in space by a SpaceX rocket, which released dozens of satellites into low-Earth orbit. 

Astronomers call this rare phenomenon a "SpaceX spiral," and expect them to become a much more common sight in the future.

On March 4, at 5:05 p.m. EST, SpaceX launched a Falcon 9 rocket from the Vandenberg Space Force Base in California. The rocket was part of the Transport-10 mission and was carrying 53 satellites belonging to several different commercial space companies, which were successfully released into orbit around our planet around two hours after launch, Live Science's sister site Space.com reported. 

Shortly after payload deployment, the rocket's second stage, which had already separated from the rocket's reusable first-stage booster, began to de-orbit and later burned up in the atmosphere above the Barents Sea in the Arctic. During this maneuver, the spinning rocket dumped its remaining fuel into space, which then froze into tiny crystals that spread out in a spiral shape and reflected sunlight to Earth. 

Related: Ethereal halo of light around full moon spotted during recent SpaceX rocket launch

Aurora photographer Shang Yang captured a stunning photo of the illuminated swirl near the town of Akureyri in Iceland at around 1 a.m. local time on March 5. "It looked otherworldly against the Northern Lights," Shang told Spaceweather.com. The spectacle lasted for around 10 minutes before dissipating.

The whirlpool of light was also captured during an aurora livestream in Iceland, and was photographed in Finland and in Norway, where it had a striking blue color. 

SpaceX spirals are rare. But they are becoming more common as the number of SpaceX launches increases.

In April 2023, a stunning blue SpaceX spiral photobombed an aurora display above Alaska. The phenomenon has also been spotted twice by a camera attached to the Subaru Telescope on Hawaii's Mauna Kea: first in April 2022 and again in January last year. 

The spirals do not appear after every launch, for several reasons — including the spin rate of the booster, time of day and the orientation of the rocket compared to Earth and the sun. This makes it hard to tell when they will be visible.

However, astrophotographer Olivier Staiger correctly predicted that the Transport-10 mission would produce a spiral above the Arctic, Spaceweather.com reported. He realized that the rocket's varied payload would require it to spin more than normal during deployment, which would mean it would still be spinning fast when it dumped its fuel.

Staiger also predicts that there will be another strong SpaceX spiral above Iceland and other parts of the Arctic when the Transporter-12 mission launches in October this year.

A spacecraft launching, a race car zipping around a track, a cheetah hurtling toward its prey — our home planet is full of high-speed feats.

But what's the fastest thing on Earth? The answer depends on how you define "thing" and "on Earth." And the top candidates — neutrinos and photons — cannot be seen with the naked eye.

The most obvious answer appears to be light. In a vacuum, light travels approximately 186,000 miles per second (300,000 kilometers per second). Nothing in the universe that we know of can exceed this speed.

Related: What is the smallest particle in the universe? (What about the largest?)

Is light a thing, though? Physicists don't fully agree on this. Some say no, because light has no mass. Others say yes — due to the quirks of quantum mechanics, light is simultaneously a wave and a particle. And most physicists agree that particles are things.

In the vacuum of space, those particles, called photons, are the fastest things, according to John Matthews, a physicist at the University of Utah.

Down on Earth, it gets a little more complicated, unless you're in a vacuum chamber. Once a photon hits Earth's atmosphere, it slows down slightly. And then, under the right circumstances, it could have some competition. That's because not all particles are slowed by the atmosphere the way photons are, Matthews told Live Science.

Matthews is part of a team that has detected several very fast particles originating from ultra-high-energy cosmic rays, showers of subatomic particles that rain down on Earth from space. One of these particles, dubbed the Oh-My-God particle, was detected by his colleagues in 1991, from the highest-energy cosmic ray that's yet to be spotted.

Particles like these start out going extremely close to the speed of light in a vacuum. But when they hit Earth's atmosphere, "by their nature, they just continue to barrel ahead," Matthews said. "So they're exceeding the speed of light in the atmosphere."

That makes the Oh-My-God particles among the fastest things with mass on Earth, but they're not at the very top. Instead, the neutrino takes that prize, per Justin Vandenbroucke, a particle physicist at the University of Wisconsin-Madison.

The Oh-My-God particle is probably a proton, or at least proton-like — fairly massive on the scale of subatomic particles. A neutrino's mass is at least 10 billion times smaller than a proton's, so thanks to the basic laws of physics, it can travel even faster if given the same amount of energy.

But while neutrinos can, in theory, go very fast, it's quite hard to pin them down in practice. "Neutrinos are famously shy," Vandenbroucke told Live Science.

In a long-term experiment at the South Pole — aptly named IceCube — physicists have placed detectors inside a 0.2-cubic-mile (1 cubic kilometer) chunk of ice, hoping to find high-energy neutrinos. Inside ice, a neutrino with enough energy can travel faster than light can. When that high-energy neutrino collides with the nucleus of an atom in the ice, it can produce charged subatomic particles also traveling faster than light. These speedy particles emit a flash of light known as Cherenkov radiation, making the neutrino indirectly detectable.

And in 2016, IceCube scientists detected the highest-energy neutrino that's been carefully evaluated yet.

"As far as we know, these are the fastest particles ever seen," Bill Louis, a physicist at Los Alamos National Laboratory, told Live Science. No particle with mass can reach the vacuum speed of light, but if it's very light and has a lot of energy, it can get very close.

Just how close? To keep the speeds straight, Vandenbroucke likes to think in terms of 9s. Something moving at 99.99% the speed of light would have four 9s. The superfast neutrino detected in 2016 would have 33 9s, Vandenbroucke said. And the Oh-My-God particle would have somewhere between 20 and 24 9s, per his calculations. This particle had more energy, but it was also much more massive.

For comparison, the fastest speeds reached by particles in human-made particle accelerators like CERN's Large Hadron Collider would have just seven 9s.

Meanwhile, these record-setting superfast particles "are produced by naturally occurring particle accelerators out in the universe," Vandenbroucke said. "We don't know how they work, but it really tells you how amazing nature is compared to humans."

The Hubble Space Telescope recently snapped an extremely rare, near-perfect ring of gravitationally warped light, known as an "Einstein ring," shining from a galaxy in the early universe. The luminous halo lines up perfectly with another galaxy, making it look like a diamond-studded engagement ring.

Einstein rings occur when light from a distant galaxy is bent around a closer galaxy or black hole that is perfectly aligned between the distant object and the observer. This bending effect, known as gravitational lensing, is caused by light passing through space-time that has been warped by the immense gravity exerted by the foreground object. The light travels in a straight line through the curved space-time, making it appear as if it were arching around the foreground object. 

In addition to bending the light, gravitational lensing magnifies it, allowing astronomers to spot distant objects that would otherwise be almost invisible to us. This effect was first predicted by Albert Einstein's theory of relativity, which is what gives the cosmic circles their name.

In the new photo, the light of the Einstein ring, named HerS J020941.1+001557, comes from a galaxy located around 19.5 billion light-years from Earth. It has been lensed by a foreground galaxy, named SDSS J020941.27+001558.4, around 2.7 billion light-years away, which is the bright dot at the center of the ring. A third non-lensing galaxy, J020941.23+001600.7, aligns perfectly with the halo of light, making it look like an affixed gemstone. 

HerS J020941 was first discovered in 2015 by the citizen science project Space Warps, but the new Hubble image shows it in a much higher resolution.

Related: Stunningly perfect 'Einstein ring' captured by James Webb Space Telescope

The galaxy emitting the Einstein ring is so far away that you might think its light should not be visible to us; at more than 19 billion light-years away, the light appears older than the universe itself, which is thought to be roughly 13.8 billion years old. However, due to the expansion of the universe, the galaxy has moved away from us while its light has traveled toward us. The light we see was first emitted from the galaxy around 11.2 billion years ago. As a result, the light has a red hue because it has been stretched out by cosmic expansion — a phenomenon known as red shift. 

HerS J02094 is one of the oldest Einstein rings ever spotted, but we have seen even more distant examples. Last year, the James Webb Space Telescope (JWST) spotted an Einstein ring around 21 billion light-years from Earth.

Einstein rings are a key area of study for astrophysicists because they can help shed light on dark matter — the invisible matter of unknown origin that makes up around 85% of the universe's mass. By measuring the size of the luminous halos, researchers can analyze the mass of the foreground galaxies, which allows them to calculate the discrepancy between their estimated mass (based on the number of stars the foreground galaxies hold) and their actual mass. That difference is caused by the presence of dark matter.  

In the coming years, JWST should help astronomers find more Einstein rings from the early universe, which will help shed even more light on the dark matter problem.

A single streak of eerily-perfect, rippling green light recently wobbled through the night sky above Iceland, interrupting an otherwise typical aurora, stunning new photos show. The extremely rare phenomenon is the result of large waves vibrating in Earth's magnetic field that are triggered by solar particles slamming into our planet.

Jeff Dai, an astrophotographer and member of The World at Night (TWAN) project, spotted the zig-zagging light show above Kerid — a crater lake in south Iceland — on Jan. 16, Spaceweather.com reported. The unusual phenomenon, known as aurora curls, lasted for "several minutes" before disappearing completely, Dai wrote on Instagram.

Auroras are created when highly energetic particles from the sun bypass Earth's magnetic field, or magnetosphere, and excite molecules of gas, which give off colored light as a result. Normally, these dancing lights swirl randomly across the night sky with no definite shape or pattern. 

Aurora curls are a rare, highly organized version of these lights caused by massive ripples in the magnetosphere, known as ultra-low frequency (ULF) waves. These magnetic tremors are most commonly triggered by a gust of radiation from the sun, known as solar wind, colliding with our planet's protective shield and can cause our atmosphere to "ring like a bell," according to Spaceweather.com. 

Normally, ULF waves are invisible and are spotted only by scientific instruments that are honed in on Earth's upper atmosphere. But in this case, the pulsations allowed solar radiation to penetrate the magnetosphere and create a singular strip of light that took the shape of the invisible waves above.

"Imagine that Earth's magnetic field is like a guitar string," Xing-Yu Li, a ULF wave expert at Peking University in Beijing, China, told Spaceweather.com. In the new picture, "we are seeing vibrations in that string."

Related: What if Earth's magnetic field disappeared?

There are several types of ULF waves, which can be split into two main groups: Pulsation irregular (Pi) waves, which have irregular wavelengths; and pulsation continuous (Pc) waves, which have a continuous wavelength.

It is not entirely clear which type of waves created the aurora curls because the magnetic tremors were not picked up by scientific equipment. Based on the images, Li estimates that the magnetic pulsations had a wavelength of around 0.6 mile (1 kilometer).

Both auroras and ULF waves are more common during periods of high solar activity. 

The sun is currently on the verge of the explosive peak in its roughly 11-year solar activity cycle, known as the solar maximum. During this time, solar storms become more frequent and powerful, and our home star spits out more intense bouts of solar wind. Therefore, there is a chance we will see more aurora curls over the next few years.

Scientists have discovered an "almost invisible" dwarf galaxy that cannot be explained by our current understanding of the cosmos. The mysteriously faint object, which has evaded detection for years, is so dim that researchers haven't even been able to pin down exactly where it is.

The newfound galaxy, named Nube (or "cloud" in Spanish), was described in a study published Jan. 9 in the journal Astronomy & Astrophysics. Nube is extremely diffuse, which means that its stars are very spread out and, as a result, the galaxy emits barely any light. It is around 10 times fainter than most other known dwarf galaxies and is more than 10 times wider than it should be considering the number of stars it has. 

"With our present knowledge we do not understand how a galaxy with such extreme characteristics can exist," study lead author Mireia Montes, an astrophysicist at the Institute of Astrophysics of the Canary Islands, said in a statement.

The researchers discovered Nube when they reanalyzed data collected by the Sloan Digital Sky Survey — one of the largest and most detailed astronomical databases of the night sky — and spotted a small inconsistency that had gone unnoticed for years. After catching the anomaly, the team took ultra-deep multicolor images of the outlying coordinates using the Green Bank Telescope in West Virginia and the Gran Telescopio Canarias in La Palma, Spain.

But even then, Nube is so faint that the team cannot accurately pin down its exact distance from our own galaxy. The researchers suspect that it is around 300 million light-years from the Milky Way, and around a third of the size across. But further observations are needed to confirm this.

Related: James Webb telescope's observations of 'impossible' galaxies at the dawn of time may finally have an explanation

The general rule of galaxy formation is that a galaxy's density is highest at the core and decreases further out. But the concentration of stars in Nube "varies very little throughout the object, which is why it is so faint," Montes said.

The researchers can't explain how the galaxy is kept together when it has so little mass at its center, which would normally exert the gravity needed to keep the rest of the stars in place. 

Normally, astronomers think such gravitational anomalies are caused by dark matter — a mysterious type of matter with unknown origins that does not react with light and supposedly makes up around 27% of the universe's mass. However, based on our current understanding of dark matter, there should not be enough of it to explain Nube's unusual properties.

"One possibility which is attractive, is that the unusual properties of Nube are showing us that the particles which make up dark matter have an extremely small mass," study co-author Ignacio Trujillo, an astrophysicist at the Institute of Astrophysics of the Canary Islands, said in the statement. If this were true, dark matter would be a "demonstration of the properties of quantum physics, but on a galactic scale," he added.

"If this hypothesis is confirmed, it would be one of the most beautiful demonstrations of nature, unifying the world of the smallest with that of the largest," Trujillo added. However, this is just one possible theory.

Whatever the cause of Nube's diffuse nature, the researchers are now on the hunt for similarly faint galaxies that could help unravel the mystery.

"It is possible that with this galaxy, and similar ones which we might find, we can find additional clues which will open a new window on the understanding of the universe," Montes said.

"Spectacular" rainbow-colored clouds have been shimmering in the skies over and around the Arctic for more than three days thanks to an unusual cold snap in the upper atmosphere. And even more of these technicolor treats could appear during the next few months, experts say.

The colorful clouds, known as polar stratospheric clouds (PSCs), were spotted floating high in the sky above parts of Norway, Sweden, Finland and Alaska, and even as far south as Scotland. They began to emerge on Dec. 18 and continued to appear clearly until Dec. 20, according to Spaceweather.com. Some smaller, less distinct clouds were also spotted on Dec. 21, but in general they seem to be disappearing. 

Photographer Ramunė Šapailaitė captured staggering photos of the rare phenomenon above Gran in southern Norway. Her photos revealed the rainbow hues of PSCs and their iridescent shimmer that has inspired the nickname nacreous clouds, due to their similarity with nacre — an iridescent material, also known as mother-of-pearl, that is found in the shells of some mollusks.

"The colors are spectacular," Šapailaitė told Spaceweather.com. "The clouds were visible in the sky all day, but the colors really exploded just before sunset."

The PSCs were caused by a prolonged period of unusually cold temperatures in the sky, according to Spaceweather.com.

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

PSCs are made from tiny ice crystals that refract, or scatter, sunlight. This separates the light into individual wavelengths, or colors, and creates the rainbow-like effect we see from the ground.

There are two types of PSCs: Type I, made from a mix of ice crystals and nitric acid, which produce less spectacular colors and are linked to the formation of ozone holes; and Type II, which are composed of pure ice crystals and produce more vivid colors. The clouds that recently formed over the Arctic were Type II.

The shimmering structures only form in the lower stratosphere, between 9.3 and 15.5 miles (15 to 25 kilometers) above Earth's surface. Normally, clouds do not form this high up in the atmosphere because it is too dry. But at extremely low temperatures — below minus 121 degrees Fahrenheit (minus 85 degrees Celsius) — widely spaced water molecules begin to coalesce into tiny ice crystals that further aggregate into clouds.

Stratospheric temperatures in the Arctic rarely drop below the threshold needed for PSCs to form, so they are normally only spotted a handful of times every year during winter months. The extreme cold snap that led to the recent appearance of PSCs may have been triggered in part by the current El Niño event, which can impact temperatures around the poles. However, human-caused climate change could also be to blame, according to Spaceweather.com.

Experts say there is a high chance that we will see more PSCs in the Arctic over the next few months, according to Spaceweather.com.

Editors note: This article was updated on Dec. 7 at 9:15 a.m. ET to correct an error that stated the halo of light was caused by the SpaceX rocket launch. The two things were not connected but do appear in the same photo.

An ethereal halo of light around the full moon created by ice crystals from overhanging clouds recently shone bright during a SpaceX rocket launch in Florida, setting the stage for a stunning time-lapse photo that captured the luminous ring and streaking rocket in the same frame.  

On Nov. 27, SpaceX launched one of its Falcon 9 rockets at 11:20 p.m. EST from Florida's Cape Canaveral Space Force Station, Live Science's sister site Space.com reported. The rocket, which was carrying 23 Starlink satellites, promptly made it out of Earth's atmosphere and safely delivered its payload into low-Earth orbit. 

At the same time, November's full moon, was also high in the sky and surrounded by a ring of light. The luminous halo was created by light reflecting off tiny ice crystals from cirrus clouds — thin and patchy clouds that form between 20,000 and 40,000 feet (6,100 and 12,200 meters) above Earth's surface, Spaceweather.com reported.

Similar light arcs and halos are also occasionally spotted around the sun when the ice crystals from cirrus clouds perfectly align between our home star and an observer.

Photographer Gilbert Plumer took a time-lapse image of the rocket launch from Rockledge, around 20 miles (32 kilometers) from Cape Canaveral. The prolonged photo shows the fiery trajectory of the ascending rocket with the halo in the background.

Related: SpaceX rockets keep tearing blood-red 'atmospheric holes' in the sky, and scientists are concerned 

The rocket also punched a hole through the icy clouds shortly after launch but this was not the cause of the halo.

It is unclear when the halo emerged but the time-lapse image spans exactly 128 seconds, which means the ring stayed intact for at least this long. 

The  number of SpaceX launches is increasing year on year as the company expands its Starlink constellation, which aims to make the internet more widely accessible across the globe. But, despite setting the stage for some cool photos, these more frequent launches may not be such a good thing, Plumer told Live Science in an email.

"The Starlink schedule has increased so much that there is a launch every week," Plumer said. The increase in orbiting satellites is making the sky much brighter than it used to be, which is already causing problems for astronomers, he added

In July, new research revealed that Starlink satellites are also "leaking" radio waves that could hinder radio astronomers too. 

The company has also been criticized because satellites can fall out of orbit and crash back to Earth during solar storms. 

Although this rocket launch was not the cause of the halo of light, Falcon 9 rockets have been linked to other visual phenomena in the past, including bright red streaks of aurora-like light that appear in the sky after the rockets open "holes" in the upper atmosphere, and whirlpool-like swirls of light, known as SpaceX spirals, which are created when frozen fuel is dumped from the rockets' spinning secondary boosters

De-orbiting SpaceX rockets are smashing temporary holes in the upper atmosphere, creating bright blobs of light in the sky. Now, scientists have warned that these "SpaceX auroras," which look like glowing red orbs of light, could be causing unrecognized problems — though they are not a threat to the environment or life on Earth.   

Researchers have known for decades that launching rockets into space can punch holes in the upper ionosphere — the part of the atmosphere between 50 and 400 miles (80 and 644 kilometers) above Earth's surface where gas is ionized, or stripped of electrons. These "ionospheric holes" can excite gas molecules in this part of the atmosphere and trigger vibrant streaks of red, aurora-like light. 

For example, in July, a SpaceX Falcon 9 rocket, which was carrying Starlink satellites into orbit, ripped open a hole above Arizona that made the sky bleed. And, in September, a U.S. Space Force rocket accidentally punched an ionospheric hole above California, which created a faint red glow.

Now, astronomers at the McDonald Observatory in Texas have spotted similar but unique red lights appearing long after SpaceX's Falcon 9 rockets have left Earth's atmosphere. These lights, which are smaller and more spherical than the long streaks created by launching rockets, are the result of ionospheric holes carved out by the rockets' secondary boosters as they fall back to Earth after detaching from the rockets, Spaceweather.com reported.

Astronomers spotted the first of these SpaceX auroras above the observatory in February, and now are seeing "2 to 5 of them each month," Stephen Hummel, an astronomer and outreach program coordinator at McDonald Observatory, told Spaceweather.com. The red orbs are "very bright" and "easily visible with the naked eye," he added.

Related: SpaceX's Starlink satellites are leaking radiation that's 'photobombing' our attempts to study the cosmos

Ascending rockets and de-orbiting boosters both trigger ionospheric holes by releasing fuel into the ionosphere, which causes ionized oxygen atoms to recombine, or turn back into regular gas molecules. 

This transformation excites the molecules and causes them to release red light, similar to when the gas is excited by solar radiation during traditional auroral displays. This essentially creates a hole in the surrounding plasma, or ionized gas. But the recombined molecules are are reionized, which closes up the holes within 10 to 20 minutes.

SpaceX's de-orbiting boosters release fuel during short burns in order to manouver the falling debris to touch down in the southern Atlantic Ocean instead of crashing onto land. The resulting holes typically form above the south-central U.S. around 90 minutes after launch at an altitude of about 185 miles (300 km), according to Spaceweather.com. These holes are smaller and more circular than the holes torn open by launching rockets, so the resulting lights are more spherical and do not linger as long. But they are appearing more frequently.

Just like the larger light shows, the ionospheric holes pose no danger to life on Earth's surface. However, "their impact on astronomical science is still being evaluated," Hummel said. As a result, it is "a growing area of attention" among researchers, he added.

Changes to the ionosphere can also disrupt shortwave radio communication and interfere with GPS signals, according to Spaceweather.com.

Studying these holes could also help scientists learn more about the ionosphere. 

"The ionospheric density is different night to night, so we can learn something about the efficiency of the [ionosphere's] chemistry by observing many events," Jeffrey Baumgardner, a physicist at Boston University, told Spaceweather.com.

Related: World's largest communication satellite is a photobombing menace, astronomers warn

The red blobs are not the only light shows created by SpaceX rockets. The company's rocket boosters spin and dump their leftover fuel in space before they de-orbit, which creates a cloud of tiny ice crystals. These crystals can occasionally reflect sunlight back toward Earth, and the illuminated fuel creates bright spirals in the night sky, known as "SpaceX spirals."

There have already been two major SpaceX spirals this year: The first was in January, which was spotted forming above Mauna Kea in Hawaii, and the second occurred in April, which shone during a traditional auroral display in Alaska.

The number of SpaceX launches is rapidly increasing so the auroras and spirals are both likely to become more common in the future.

Scientists recently filmed a super-rare, ultra-black anglerfish lurking like a living shadow in the deep sea off the California coastline. 

Researchers from the Monterey Bay Aquarium Research Institute (MBARI) spotted the unidentified species of dreamer anglerfish (genus Oneirodes) on Sept. 29. They filmed it 2,562 feet (781 meters) below the surface while maneuvering a remotely operated vehicle (ROV) in Monterey Canyon — a massive deep-sea canyon that spans more than 292 miles (470 kilometers) off the California coast. 

The researchers were collecting tiny, spiked organisms known as phaeodarians, which float in the water column and eat falling detritus, or marine snow, when they came across the football-size female fish. It is the first dreamer anglerfish seen in Monterey Canyon since 2016 and only the ninth time scientists have spotted these creatures in the area over the last 36 years, according to an MBARI statement.

"Coming upon a lurking anglerfish is an exciting experience for anyone exploring the deep water column," Bruce Robinson, a senior scientist at MBARI, said in the statement.

A video of the encounter clearly shows marine snow swirling around the evolutionary oddity, but little is visible beyond its distinctive outline. That's because its skin is so dark it absorbs light and acts like an "invisibility cloak," Robinson said. 

Related: Why do deep-sea fish look like aliens?

This species of dreamer anglerfish belongs to an exclusive club of "ultra-black" deep-sea creatures, which absorb at least 99.5% of the light that hits them. Fifteen other marine species are known to absorb this much light, according to a 2020 study published in the journal Current Biology. 

These animals are so dark that "it's like looking at a black hole," study lead author Alexander Davis, a marine ecologist at Duke University and MBARI, told The New York Times when the 2020 study was released.

The study revealed that these animals' skin is tightly packed with melanosomes — cells containing the pigment melanin, which also gives human skin its color. The shape and configuration of these cells enable them to absorb almost every wavelength of light that hits the creatures' skin. 

"Ultra-black skin ensures that any light that hits you, even the bright light from your own streetlamp-like lure, is completely absorbed — nothing reflects back to expose your location," study co-author Karen Osborn, a zoologist at the Smithsonian National Museum of Natural History and MBARI, said in the statement. 

This enables dreamer anglerfish to remain completely hidden as they "lie secretly in wait for their prey" while using their fishing rod-like bioluminescent lures, Robinson said. 

The curious camouflage also helps the dreamers to hide from predators. When the MBARI team first spotted the anglerfish, it was using its lure. But it swiftly turned off its light when it realized it was being watched. 

Related: 10 bizarre deep sea creatures found in 2022

Scientists know the anglerfish in the new video is a female because of its size: Female dreamers can grow up to 15 inches (37 centimeters) long, while the males only grow to around 0.5 inch (1.3 cm) long. 

In addition to being a good place to spot anglerfish in the wild, California is one of the few places where anglerfish also wash up on shore.

On Oct. 17, another pitch-black female anglerfish, known as a Pacific footballfish (Himantolophus sagamius) washed ashore at Crystal Cove State Park in southern California. This was the second time the species washed up at this location, following the discovery of another female near the same spot in 2021.

Altitudes, landscapes and climates change dramatically as you move across the globe, but one factor remains nearly ubiquitous. All of Earth's diversity is blanketed under a blue sky. But why is the sky blue? It's not a reflection of Earth's oceans. The real explanation requires a bit of particle physics.

We see blue above us because of how light from the sun interacts with Earth's atmosphere. The visible light spectrum contains a variety of colors, ranging from red light to violet. When all of the colors are mixed, the light appears white, Marc Chenard, a meteorologist at the National Weather Service, told Live Science. But once the white light traveling from the sun reaches Earth, some of the colors begin to interact with molecules and small particles in the atmosphere, he said.

Each color in the visible light spectrum has a different wavelength. Red and orange light waves, for instance, have longer wavelengths, while blue and violet light have much shorter wavelengths. It's the shorter wavelengths of light that are more likely to be scattered — or absorbed and re-emitted in a different direction — by the air and gas molecules in Earth's atmosphere, Chenard said. The molecules in the atmosphere, largely nitrogen and oxygen, scatter the blue and violet light in every direction through a phenomenon called Rayleigh scattering. That's what makes the sky blue.

Related: Why is the color blue so rare in nature?

Even though violet light is scattered too, there are a couple of reasons why we see the sky as more blue than purple, according to Ed Bloomer, an astronomer at the Royal Observatory Greenwich in the U.K. First, the sun doesn't produce equal illumination in all colors; it contains more blue light than violet light, so more blue light is scattered. Additionally, our eyes are not equally responsive to all colors, Bloomer told Live Science; they are less sensitive to violet light, meaning we are more likely to see blue hues than purple ones.

This preferential scattering of blue light also plays into the colors of sunrise and sunset. At sunset, as a particular point is turning farther and farther from the sun, sunlight must travel farther through the atmosphere to reach your eyes. By the time the sunlight reaches you, all of the blue light has been scattered away. As a result, the orange, red and yellow wavelengths are all that's left to color the sunset.

The vast blue sky is produced by a combination of factors, Bloomer said. If you were on another planet, you might be looking up at a totally different color, depending on the molecules in the alien world's atmosphere, the particles of dust swirling around or the spectrum of light coming from a nearby star.

A recent solar storm smashed into Earth and created what appeared to be bright pumpkin-colored pillars dancing in the night sky above Canada, a haunting new photo reveals. But there is a problem with the image: Orange-colored auroras should not exist. 

Instead of impossible auroras, the image actually captured a rare mix of red and green lights that hasn't been this visible since a monstrous Halloween solar storm smashed into Earth 20 years ago, experts say. 

"The orange was sublime, just incredible," aurora photographer Harlan Thomas told Spaceweather.com. "The pillars in the center stayed there glowing for more than 20 minutes."

Thomas captured the colorful shot on Oct. 19 above a pond to the west of Calgary in Alberta, around three days after the sun launched a hefty, slow-moving coronal mass ejection (CME) toward Earth. 

Related: 10 bizarre phenomena that lit up the sky (and their scientific explanations)

Auroras are created when high-energy particles from CMEs or solar wind bypass Earth's magnetic shield, or magnetosphere, and superheat gas molecules in the upper atmosphere. The excited molecules release energy in the form of light, and the color of that light depends on which element is being excited. The two most common aurora colors are red and green, which are both given off by oxygen molecules at different altitudes (red auroras are produced at higher altitudes than their green variants). But when the solar particles penetrate deep into the atmosphere, they can also trigger rare pink auroras when they excite nitrogen molecules.

Theoretically, both oxygen and nitrogen molecules can give off orange wavelengths under specific conditions. However, even when this happens, the orange is overwhelmed by the other colors given off by the molecules surrounding it, making it practically impossible to see these wavelengths, Spaceweather.com reported.

So how do we see this color in the latest image?

"There can be a mixing of the two processes [red and green auroras], which fools the camera and eye to believe that it is orange," Kjellmar Oksavik, a space weather scientist and aurora expert at the University of Bergen in Norway, told Spaceweather.com. "In reality, it is both red and green at the same time."

Despite red and green auroras frequently occurring together in the sky, "orange" auroras are very rare. The orange color is most visible at the center of large auroral rays — vertical pillars of light that align along invisible magnetic field lines — that are made up of both red and green light, which are very uncommon, Oksavik said.

The last time such vibrant pumpkin-like hues were spotted was the great Halloween storm of 2003 — the most powerful solar storm in modern records, Spaceweather.com reported. During this epic event, the orange lights were spotted across North America and northern Europe.

Scientists at the world's largest gravitational wave observatory have just squeezed light beyond a key quantum limit.

The new technique, called frequency-dependent squeezing, will increase the number of tiny ripples in space-time detectable by the Laser Interferometer Gravitational-Wave Observatory (LIGO), boosting the number of neutron star and black hole collisions the detector can find. 

Related: Quantum 'yin-yang' shows two photons being entangled in real-time

"Now that we have surpassed this quantum limit, we can do a lot more astronomy," co-lead author Lee McCuller, an assistant professor of physics at Caltech, said in a statement.Gravitational waves ripple out when objects with mass move through space. Bigger objects — such as neutron stars or black holes — produce more prominent gravitational waves. Scientists first detected these space-time ripples in 2015 and have steadily gotten better at spotting the waves as they lap at our cosmic shores.

The LIGO detector spots these cosmic ripples from the way they distort space-time as they pass through it. Made up of two intersecting L-shaped detectors — each with two 2.48-mile-long (4 kilometers) arms and two identical laser beams inside — the experiment is designed such that if a gravitational wave passes through Earth, the laser light in one arm of the detector will get compressed while the other expands, creating a tiny change in relative path lengths of the beams arriving at the detector.

But because these distortions are so tiny — often the size of a few thousandths of a proton or neutron — LIGO's detectors must be incredibly sensitive. So sensitive, in fact, that their most precise measurements are muddied by noise from quantum effects, or the spontaneous interactions of subatomic particles.

High frequency noise comes from tiny particles randomly popping in and out of existence. Low frequency noise comes from the rumble of reflecting light particles that cause the mirrors to wobble. Both sources  limit the number and types of gravitational waves LIGO can detect.

To break through these quantum limitations, the physicists turned to another principle of physics: Heisenberg's uncertainty principle, which states that we can only simultaneously know specific pairs of a particle's physical properties to a set level of certainty.

This means that there is a trade-off in how well scientists can measure both the amplitude (or power) and frequency of the light inside LIGO, but it also means that either property can be amplified at the cost of the other. By using crystals that split individual photons, or packets of light, into two entangled photons, the physicists tuned the light so that the uncertainty behind its amplitude or its frequency could be "'squeezed"' as required.

Frequency-dependent squeezing works a bit like pinching a balloon, the researchers say. Just as pinching a balloon at one end helps the other end get bigger, pinching one property of light to know it with greater certainty moves the overall uncertainty to the other. This means that at low frequencies, a squeezed amplitude reduces noise from the mirror rumbling, and at high frequencies a squished phase makes the signal stronger than noise from quantum perturbations.

"It is true that we are doing this really cool quantum thing, but the real reason for this is that it's the simplest way to improve LIGO's sensitivity," co-lead author Dhruva Ganapathy, a graduate student at MIT, said in the statement. "Otherwise, we would have to turn up the laser, which has its own problems, or we would have to greatly increase the sizes of the mirrors, which would be expensive."

The findings were published Sept. 6 in the journal Physical Review X.

Photos snapped by the James Webb Space Telescope (JWST) have revealed the farthest-ever example of an "Einstein ring." The record-breaking halo of warped light, which is a whopping 21 billion light-years away, is unusually perfect and surrounds a mysteriously dense galaxy.

An Einstein ring is an extremely rare type of gravitationally lensed object that was first predicted by Albert Einstein's theory of relativity. Gravitational lensing occurs when the immense gravity of a massive foreground object, such as a galaxy cluster or a black hole, warps space-time around itself; light emitted by more distant objects, such as galaxies or supernovas, that passes through this warped space-time also appears curved and warped from our perspective on Earth.

This effect also magnifies the light of the object being lensed, similar to how a magnifying glass works, allowing astronomers to study distant objects in greater detail than is normally possible. Most gravitationally lensed objects form arcs or partial rings that surround the foreground object. But a true Einstein ring forms a complete circle around the closer entity, which is possible only when the distant object, foreground object and observer are perfectly aligned.

In a new study uploaded Sept. 14 to the preprint server arXiv and accepted for publication in the journal Nature Astronomy, researchers discovered the new eerily circular Einstein ring, named JWST-ER1, within the COSMOS-Web survey, a detailed map of more than 500,000 galaxies captured during a 200-hour continuous JWST observation.

JWST-ER1 has two parts: JWST-ER1g, the compact galaxy that acts as the lensing object in the foreground; and JWST-ER1r, the light from a more distant galaxy that forms the luminous ring. JWST-ER1g is located around 17 billion light-years from Earth, while JWST-ER1r is another 4 billion light-years farther away. Until now, the farthest detected lensing object was around 14.7 billion light-years away, according to BigThink.com. (While the age of the universe itself is estimated to be about 13.7 billion years, the universe's constant expansion means that light from the oldest objects must travel much farther than this to reach our telescopes).

Related: Dark matter's secret identity could be hiding in distorted 'Einstein rings'

Thanks to the complete ring of JWST-ER1, researchers calculated the mass of the lensing galaxy by seeing how much it had warped space-time around itself. This revealed that the galaxy has a mass equivalent to around 650 billion suns, which makes it unusually dense for its size. Some of this extra mass can be explained by dark matter, the mysterious, invisible matter that makes up around 85% of all matter in the universe. But even then, it is unlikely that there are enough stars to account for the rest of the galaxy's heft based on the researchers' calculations.

"Additional mass is needed to explain the lensing results," but it is not exactly clear what this mass is, the researchers wrote in the paper.

Other, similarly old and equally dense galaxies have been detected before, which suggests there is something common about these ancient star factories that makes them so massive. One explanation is that these galaxies harbor much more dark matter than expected, while another theory suggests that they may have more small-mass stars lurking within them than younger galaxies do. But more work is needed to find out.

This is not the first true Einstein ring spotted by JWST. In September 2022, a Reddit user discovered a perfectly circular ring of light from the galaxy JO418, located around 12 billion light-years from Earth, lensed around a closer galaxy.

JWST has also utilized gravitational lensing to snap the most distant star ever detected and one of the universe's oldest galaxies.

A SpaceX rocket recently punched a hole in Earth's upper atmosphere while venturing into space, leaving behind a blood-red streak of light in the sky similar to an aurora.

The Falcon 9 rocket, which was carrying 15 SpaceX Starlink satellites into orbit, lifted off from Vandenberg Space Force Base in California on July 19 at around 9 p.m. PDT, according to Live Science's sister site Space.com. As the rocket rose into the upper atmosphere, its exhaust plume became illuminated by sunlight, which created a stunning spectacle seen across California and parts of Arizona. But what followed was even more awe-inspiring.

"After the rocket passed overhead, a red fluorescent glow expanded southward and crossed over with the Milky Way [in the sky]," Jeremy Perez, a photographer based in Flagstaff, Arizona, told Spaceweather.com. Perez captured several epic shots of the "fluorescent red glow" from his vantage point at the San Francisco Volcanic Fields, located north of Flagstaff. The light show lasted around 20 minutes, he added.

The unusual red light was the result of the rocket disrupting the ionosphere, the part of Earth's atmosphere where gases are ionized, or lose electrons, and turn into plasma. The ionosphere stretches between roughly 50 and 400 miles (80 and 644 kilometers) above Earth's surface, according to NASA. This is a previously known phenomenon, but the latest episode is one of the most vivid examples to date, Spaceweather.com reported.

Related: SpaceX's Starlink satellites are leaking radiation that's 'photobombing' our attempts to study the cosmos

"Ionospheric holes" are created when a rocket's second stage burns fuel between 124 and 186 miles (200 and 300 km) above Earth's surface, Jeffrey Baumgardner, a physicist at Boston University, told Spaceweather.com. At this height, the carbon dioxide and water vapor from the rocket's exhaust cause ionized oxygen atoms to recombine, or form back into normal oxygen molecules, which excites the molecules and causes them to emit energy in the form of light, he added.

This is similar to how auroras form, except the dancing lights are caused by solar radiation heating up gases rather than recombining them. The holes pose no threat to people on the surface and naturally close up within a few hours as the recombined gases get re-ionized.

Scientists have known that rockets can trigger these sorts of effects since at least 2005, when a Titan rocket triggered "severe ionospheric perturbations" that were equivalent to a minor geomagnetic storm. But they are becoming more common. 

In August 2017, a Falcon 9 rocket created a hole four times bigger than the state of California, the largest ever recorded. And in June 2022, another Falcon 9 punched a hole over the U.S. East Coast, sparking a display of red lights from New York to the Carolinas that many observers mistook for the northern lights, Spaceweather.com reported at the time.

As the number of rocket launches, particularly by private companies such as SpaceX, continues to increase in the coming years, it is likely that these ionospheric holes and their associated light shows will become much more common, according to Spaceweather.com.

Photographers in the Mediterranean recently captured stunning images of the sun appearing to melt toward the horizon as it set one day and then rose again the next day, creating trippy "lava-like blobs" in the sky. 

On both occasions, an enormous sunspot was also clearly visible on the warped sun's surface.

On July 11, photographer Martin Gembec captured shots of the oozing sun from the island of Korčula in Croatia as the seemingly deformed star began to set behind the Adriatic Sea. Then on July 12, photographer David Marshall saw the same effect as the sun rose above the Adriatic Sea, but this time from the Italian coastline near San Benedetto del Tronto.

The rare phenomenon is known as the "Omega sun" — named after the Greek letter, which has a similar shape to the warped sun that stretches down and then out, according to Spaceweather.com. It is a type of "inferior mirage," which is caused by differences in air temperature above the water's surface. The effect is also dubbed the "Etruscan vase" due to the similarities between the shape of the warped sun and pottery made in what is now Italy between the 7th and 5th centuries B.C..

The images by Gembec (seen above) are only a partial Omega sun because the setting sun does not touch and spill out across the horizon. Marshall's photo (seen below) shows the phenomenon in its entirety as the sun rises from behind Earth's curvature. 

Related: Ethereal 'halo' and light arcs around the sun captured in photos of ultra-rare phenomena

Inferior mirages are created when the ocean's surface, and the air just above it, is much warmer than the air further above the surface. The temperature difference causes light from an object (in this case the sun) to bend upward toward an observer, which counterintuitively creates a second inverted image of the object underneath, according to San Diego State University. So during an Omega sun, the bottom part of the sun is essentially being reflected by an invisible mirror. (The same mirage can also sometimes warp the moon in a similar way if it is near the horizon.)

As the sun sets, the last part of the sphere that dips below the horizon can also be warped into a triangle, making it look more like a pyramid (see below).

The opposite of an inferior mirage, known as a superior mirage, is created by reverse conditions, where the temperature higher above the ocean is warmer than the air just above the water’s surface. This can cause objects, such as large boats, to appear as if they are levitating above the horizon.

The successive sightings of Omega suns in the Mediterranean may be linked to an extreme heatwave in Europe, which has caused temperatures to skyrocket to near-record levels for more than a week, according to the BBC. This excess heat could have been absorbed within the first few feet of the ocean's surface, which would cause the air around it to remain warm as temperatures cooled overnight.

In both images, a large sunspot, named AR3363, is clearly visible. On July 15, AR3363 spat out a cloud of fast-moving magnetized plasma, known as a coronal mass ejection (CME) that combined with another CME to form a "cannibal CME," which slammed into Earth on July 18.

NASA's Curiosity rover recently snapped a stunningly detailed "postcard" of the Martian landscape, showing the sunlight shifting between morning and afternoon. The wandering robot beamed the picturesque scene back to Earth shortly after waking up from a "brain boosting nap."

The rover captured the memento April 8, or Sol 3,794 (Martian days) of its mission, shortly before leaving the Marker Band Valley, a region where it discovered signs of an ancient lake in 2022. The photoshoot was one of the first actions Curiosity completed after hibernating for a software update between April 3 and April 7, which included 180 individual upgrades — the most important of which will allow the rover to process images of its surroundings faster and reduce wear on its tires, which will help it to move much quicker across the Martian landscape, Live Science's sister site Space.com reported.  

The new panorama is a composite of two images, one taken in the morning and the other in the afternoon. Combining the light of the sun from two different angles creates an image with much greater detail than a standard photograph, NASA representatives wrote in a statement.

Related: Curiosity rover discovers that evidence of past life on Mars may have been erased

"Anyone who's been to a national park knows the scene looks different in the morning than it does in the afternoon," Doug Ellison, an engineer at NASA's Jet Propulsion Laboratory in Southern California who runs Curiosity's camera team, said in the statement. "Capturing two times of day provides dark shadows because the lighting is coming in from the left and the right, like you might have on a stage – but instead of stage lights, we're relying on the Sun."

The original image is actually black and white, but color has been added to highlight the rock formations and to mimic the color of the sky during morning and afternoon.

This is the second time that Curiosity has captured an image in this way. The rover also snapped a similar split-time photo in November 2021. However, the latest postcard is much more detailed than its first attempt, likely because the photo was snapped during Mars' winter when there is less atmospheric dust, Ellison said. (The rover rarely takes images like this because the rover would need to remain in one place all day, which limits how much data it can collect.) 

The new postcard is not the only spectacular scene that Curiosity has recently snapped. In February, the rover captured one of the clearest-ever images of "sun rays," a phenomenon caused by the sun's rays shining through clouds while the sun is below the horizon, on the Red Planet. 

In addition to grand landscape shots, the rover has also turned its camera downward to shoot some up-close shots of interesting mineral formations. In February 2022, the rover caught a glimpse of a flower-like mineral and, on April 15 this year, it spied a tiny rock in the shape of a book.

A scientist recently snapped a series of shining arcs and halos of light surrounding the sun in the sky above the U.K., including an exceptionally rare ring of light that circled the entire sky.

Alan Fitzsimmons, an astronomer at Queen's University Belfast in Northern Ireland, captured the unusual light show above Belfast's Botanic Gardens on May 28. The display lasted around 30 minutes, Fitzsimmons told Live Science.

Some of the bizarre glowing rays were also spotted across other parts of Northern Ireland, as well as in northern England and Scotland, according to Spaceweather.com.

The arcs and halos are caused by millions of tiny, perfectly positioned ice crystals in the upper atmosphere, which often accompany thin cirrus clouds, Fitzsimmons said. "If the winds are very uniform up there, the hexagonal-shaped crystals align," he added. "This allows the sunlight refracting through them to combine, just as light refracts through a prism, producing arcs and circles of sunlight."

Related: Photographers capture the exact moment a gargantuan storm blasts out of the sun during a total solar eclipse

Fitzsimmons' image includes at least three different confirmed optical phenomena: a 22-degree halo, the large circle surrounding the sun; a pair of "sundogs," the bright points on each side of the 22-degree halo; and a complete parhelic circle, the line that bisects the circle, which also forms a full circle around the entire sky. 

A full parhelic circle is very rare because it requires at least five internal reflections from millions of individual ice crystals, all catching sunbeams simultaneously, according to Spaceweather.com.

The images also may include features of a circumscribed halo and a supralateral arc, which form the "eyelids" above and below the 22-degree halo, according to Spaceweather.com.

The parhelic circle is the rarest and most "impressive feature" in the image, Fitzsimmons said. It is something he has seen only a couple of times before, he added. But the other phenomena are more common than most people realize.

"The sun can be quite bright when they [the phenomena] are visible, so to notice them, you need to block out the sun with your thumb or a tree," Fitzsimmons said. "But anytime it's sunny with high-altitude wispy clouds, it's worth taking a look to see if there is a halo or maybe something more."

On May 30, a photographer in Finland also caught a shot of a rainbow-colored ring of light, known as a pollen corona, surrounding the sun. These rings, which are created by light scattering off of pollen grains in the air, are also hard to spot unless part of the sun's light has been blocked out.

Tiny atmospheric ice crystals can also create a range of other weird visual phenomena, such as polar stratospheric clouds, which shine like rainbows in the Arctic, and night-shining clouds (also called noctilucent clouds), which will become more visible to people in the Northern Hemisphere during June and July.

Something was in the air recently when a photographer in Finland snapped a stunning shot of concentric rainbow-colored rings around the sun. And it turns out that something was pollen. 

Mikko Peussa captured the eye-catching images on May 30 near his home in Turku. The multicolored rings are called "pollen coronas" and are caused by sunlight scattering off pollen in the air, according to Spaceweather.com. The star-like sparkles that appear in and around the shining rings are individual pollen grains, which can vary in size.

The effect is created by sunlight scattering, or separating into its individual wavelengths, when it hits the pollen's surface. Some of the wavelengths interfere with or crash into one another, so only certain colors reach the observer, according to Universe Today. This is known as a diffraction pattern.

Related: Photographers capture the exact moment a gargantuan storm blasts out of the sun during a total solar eclipse 

The pollen in the images comes from pine trees (Pinus sylvestris). Under the microscope, these pollen grains look like tiny "Mickey Mouses." Their "ears" are actually a pair of air pockets that help the grains float in the wind. The air sacs align in the same direction in the wind, which helps to create the diffraction pattern and causes the rings to have a slightly elliptical shape, according to Spaceweather.com.

Pollen coronas only appear when pollen concentrations are very high and can only be clearly seen when the sun or the full moon is partially obscured. Photographers like Peussa often use filters to block out additional light and make the colors stand out more than they normally would on a sunny day.

The kaleidoscopic circles sometimes have small bumps that extend further away from the sun than the rest of the ring, but experts are unsure exactly what causes this, according to Universe Today. (None of these bumps are visible in the new images).

Pine pollen is also known to create a much larger but equally unusual visual phenomenon. In January, researchers revealed that large swarms of the tiny grains created massive algae-like sea swirls on the surface of the Baltic Sea in Poland. 

Research suggests that pollen concentrations and the length of pollen seasons are increasing as a result of increased atmospheric carbon dioxide from human activity. So, pollen coronas could become a more common occurrence in the future.

Moray eels that lurk in gloomy, underwater caves appear to be adjusting to the darkness by growing skin over their eyes.

The newly described bean-eyed snake moray (Uropterygius cyamommatus) is the first moray eel species known to inhabit anchialine caves — caves carved into volcanic or limestone rock that are connected to the ocean and whose water levels fluctuate with the tides. During expeditions to Christmas Island, Australia, and Panglao Island in the Philippines, scientists found two specimens that had no visible left eyes, suggesting that the eels may be adapting to their gloomy environment by going blind, one eye at a time.

"Only two specimens from Christmas Island have reduced left eyes and we are not able to know if it is natural or if they just damaged their eyes after being born," said Wen-Chien Huang, a doctoral student of marine biotechnology at the National Sun Yat-sen University in Taiwan and the lead author of a study published March 29 in the journal Raffles Bulletin of Zoology. "But the proportions of their eyes is the smallest that we have ever seen in moray eels, so we speculate it might be the result of adaptation to the aphotic or low-light environment," Huang told Live Science in an email.

Cave explorers first trapped bean-eyed snake morays on Panglao Island in 2001, and several specimens are housed in the Lee Kong Chian Natural History Museum in Singapore, Huang said. But until now, nobody had recognized them as their own species. A 2014 study in the Raffles Bulletin of Zoology incorrectly listed a bean-eyed snake moray that researchers had caught on Christmas Island as Echidna unicolor, a fish known as the unicolor or pale moray.

The two species are both a uniform brown color, but as its name suggests, the bean-eyed snake moray has "tiny bean-shaped eyes" and a longer tail with more vertebrae than the pale moray, the researchers wrote in the new study. Whereas pale morays have been found in coral reefs in the Pacific and Indian oceans, bean-eyed snake morays have only been spotted in a handful of caves on Christmas and Panglao islands.

Related: Does evolution ever go backward? 

Researchers caught the most recent specimens more than 10 years ago with baited traps and pickled them in alcohol to preserve them. It's unclear why or when bean-eyed snake morays retreated into the gloomy cave depths, but the authors of the new study suspect it could be linked to their voracious appetites. "I think one of the reasons they went to inhabit caves is the food source, since there are abundant crustaceans inside the caves," Huang said. The scientists who caught them reported that the "greedy" eels hungrily devoured the bait they used to lure them.

For the new study, Huang and his colleagues analyzed nine specimens collected between 2001 and 2011. Two of them had "a reduced left eye embedded in skin," with no apparent change in the underlying bone structure. The researchers think they may have captured evolution in action and that, in the absence of light, skin encroaching on the eels' eyes could save them the high energetic cost associated with eyesight. 

It is not unusual for cave-dwelling fish to go entirely blind, and many of the nearly 300 fish species that live in caves have done so. A species closely related to the bean-eyed snake moray, the few-vertebrae moray (U. oligospondylus), has similarly reduced eyes and lurks in the shadows between wave-crashed boulders, where it relies on its sense of smell to detect prey.

Scientists are still unsure exactly why skin is growing over the eels' eyes and whether this potential adaptation to their cave habitat is spreading among the population. Due to the low number of preserved specimens, researchers haven't performed genetic and other molecular testing to answer these questions, Huang said. "These are issues that we are interested in, but can only be resolved when more fresh specimens are available."

Gravity can turn itself into light, but only if space-time behaves in just the right way, a research team has found.

Under normal circumstances, you cannot get something from nothing. Specifically, the Standard Model of particle physics, the reigning theory that explains the subatomic zoo of particles, usually forbids the transformation of massless particles into massive ones. While particles in the Standard Model constantly change into each other through various reactions and processes, the photon — the massless carrier of light — cannot normally change into other particles. But if the conditions are just right, it is possible — for example, when a photon interacts with a heavy atom, it can spontaneously split off to become an electron and a positron, both of which are massive particles.

With this well-known example in hand, a team of theoretical physicists, writing in a paper posted March 28 to the preprint database arXiv, asked if gravity itself could transform into other particles. We normally think of gravity through the lens of general relativity, where bends and warps in space-time influence the motion of particles. In that picture, it would be very difficult to imagine how gravity could create particles. But we can also view gravity through a quantum lens, picturing the gravitational force as carried by countless invisible particles called gravitons. While our picture of quantum gravity is far from complete, we do know that these gravitons would behave like any other fundamental particle, including potentially transforming.

To test this idea, the researchers studied the conditions of the extremely early universe. When our cosmos was very young, it was also small, hot and dense. In that youthful cosmos, all forms of matter and energy were ramped up to unimaginable scales, far greater than even our most powerful particle colliders are capable of achieving. 

The researchers found that in this setup, gravitational waves — ripples in the fabric of space-time generated by collisions between the most massive cosmic objects — play an important role. Normally, gravitational waves are exceedingly weak, capable of nudging an atom through a distance less than the width of its own nucleus. But in the early universe, the waves could have been much stronger, and that  could have seriously influenced everything else.

Those early waves would have sloshed back and forth, amplifying themselves. Anything else in the universe would have gotten caught up in the push and pull of the waves, leading to a resonance effect. Like a kid pumping their legs at just the right time to send a swing higher and higher, the gravitational waves would have acted as a pump, driving matter into tight clumps over and over again.

The gravitational waves could also affect the electromagnetic field. Because the waves are ripples in space-time itself, they don't limit themselves to interactions with massive objects. As the waves continue to pump, they can drive radiation in the universe to extremely high energies, causing the spontaneous appearance of photons: gravity generating light itself.

The researchers found that in general, this process is rather inefficient. The early universe was also expanding, so the standard patterns of gravitational waves would not have lasted long. However, the team found that if the early universe contained enough matter that the speed of light was reduced (the same way light travels more slowly through a medium such as air or water), the waves could have stuck around long enough to really get things going, generating floods of extra photons.

Physicists do not yet fully understand the complicated, tangled physics of the early universe, which was capable of achieving feats never observed since. This new research adds one more strand to the rich tapestry: the capability for gravity to create light. That radiation would presumably then go on to influence the formation of matter and the evolution of the universe, so working out the full implications of this surprising process could lead to new revolutions in our understanding of the earliest moments of the cosmos.

Scientists using tiny optical tweezers have played the world's smallest game of catch — throwing and catching individual atoms using light. 

The feat, achieved with highly-focused laser beams that held atoms in place before launching them, is the first time that atoms have been thrown from one pair of optical tweezers to another. The researchers describe the achievement in a paper published Mar. 9 in the journal Optica.

"The freely flying atoms move from one place to the other without being held by or interacting with the optical trap," co-author Jaewook Ahn, a physicist at the Korea Advanced Institute of Science and Technology in Daejeon, South Korea, said in a statement. "In other words, the atom is thrown and caught between the two optical traps much like the ball travels between the pitcher and a catcher in a baseball game."

Related: 1st 'atom tornado' created from swirling vortex of helium atoms

To send their particles flying, the physicists cooled rubidium atoms to near absolute zero temperatures before placing them inside one of two optical tweezers, which secured the atoms in place with a laser beam. Then, by accelerating the tweezers holding the atom before abruptly switching them off, the researchers launched the rubidium atom over a distance of 4.2 micrometers (less than a quarter of the width of a human hair) at speeds up to 25 inches (65 centimeters) per second. An adjacent pair of optical tweezers then caught the atoms after each throw, stopping them completely.

The researchers fleshed their method out further with a series of proof-of-principle experiments. They showed that the atoms could be thrown unimpeded through stationary optical tweezers holding other atoms, and could even be thrown precisely to form perfect arrays of atoms inside the receiving tweezer. Free-flying atoms hit their target 94% of the time; the researchers are now working to bring that up to 100%.

The physicists say their demonstration could be used to develop faster quantum computers capable of switching out information in arrays of atoms at rapid speed.

"These types of flying atoms could enable a new type of dynamic quantum computing by allowing the relative locations of qubits — the quantum equivalent to binary bits — to be more freely changed," said Ahn. "It could also be used to create collisions between individual atoms, opening a new field of atom-by-atom chemistry."

An eerily-perfect "whirlpool" of light in the shape of a spiral galaxy briefly appeared in the night sky above Hawaii. 

But what was it?

It turns out the stunning spiral was comprised of frozen rocket fuel that was ejected during a SpaceX launch.

A video of the ethereal light show was captured Jan. 18 by the Subaru-Asahi Star Camera — co-owned by the National Astronomical Observatory of Japan (NAOJ) and Japanese news agency Asahi Shimbun — attached to the Subaru telescope on top of Mauna Kea, a dormant volcano on Hawaii's Big Island. In the sped-up footage, a small blob of light unfurls into a perfect glowing whirlpool that moves across the sky for several minutes before fading away into nothingness. 

"The spiral seems to be related to the SpaceX company's launch of a new satellite," NAOJ representatives wrote on Twitter.

Related: Bizarre blue blobs hover in Earth's atmosphere in stunning astronaut photo. But what are they?

The SpaceX launch in question was a Falcon 9 rocket that successfully lifted off from Cape Canaveral Space Force Station in Florida at 7:24 a.m. EST (1224 GMT) carrying a new GPS satellite for the U.S. Space Force, Live Science's sister site Space.com reported. 

The rocket's first stage, which provides the main propulsion for lift off, separated from the payload-carrying second stage around 3 minutes after launch and eventually returned to Earth. After separating from the first stage, the second stage used its small engine to propel itself into position to deploy the satellite. Once the satellite was deployed, any remaining fuel was then ejected before reentry, which caused the second stage to enter a spin before deorbiting and falling down to Earth in the Pacific ocean. The result was a cloud of frozen fuel crystals in the shape of a spiral, which were illuminated by sunlight, according to Spaceweather.com. 

This is not the first time that SpaceX rockets have caused dazzling light shows. In April 2022, the Subaru-Asahi Star Camera captured a shimmering spiral of light after SpaceX launched a spy satellite into orbit on another Falcon 9 rocket.  

The so-called "SpaceX spirals" are becoming "commonplace over the Pacific" because this is where most Falcon 9 rocket stages fall back to Earth, Spaceweather.com representatives wrote. 

Frozen rocket fuel has also created several other stunning visual anomalies in other parts of the globe. In March 2022, frozen fuel from a Chinese rocket created a large spinning orb of light that photobombed an aurora borealis in Alaska. In October 2017, an even larger blue orb was seen in the sky above Siberia, according to ScienceAlert. On that occasion, Russian military rocket tests left the frozen fuel in the area.

A rare green comet, which has been streaking across the night sky as it approaches Earth for the first time since the Stone Age, briefly grew a bizarre third tail. This "anti-tail" appeared to streak in the wrong direction, seemingly breaking the rules of physics. 

The comet — named C/2022 E3 (ZTF) but more commonly referred to as the "green comet" thanks to a chemical reaction that emits a greenish glow around the cosmic cannonball — was first discovered in March 2022 heading towards Earth from the Oort Cloud, a collection of icy objects in the outer solar system. 

Normally, comets like this have two tails: one made from dust, which is blown off the comet by solar wind; and one made of gas from within the comet that sublimates, or transitions, directly from solid to gas. But on Jan. 21, several astrophotographers, including Ruslan Merzlyakov in Denmark and Alessandro Carrozzi in Italy, snapped pictures of the green comet with a third tail that was pointed towards the sun instead of away from it.

This bizarre third tail is known as an "anti-tail," and although it is made up from the same stuff as the comet's other tails, it is not actually part of the comet. Instead, it's an optical illusion caused by Earth moving through the comet's orbital plane, according to Spaceweather.com.

Related: Blazing comet tail is whipped by solar winds in astonishing astronomy photo 

A comet's twin tails are often clearly visible — the dust tail reflects sunlight, while the gas within the other tail becomes ionized, giving it a faint glow.  

The released gas eventually cools and becomes invisible, but the leftover dust is left to drift in the wake of the comet's trajectory around the sun, or orbital plane. When Earth crosses through a comet's orbital plane, some of this dust is reilluminated by the sun and appears as a bright streak, which can appear to shoot out of the comet in the opposite direction to its other tails, depending on the comet's trajectory and orientation. But in reality, this is just an optical illusion, and there is no extra tail.

This illusion is similar to how the Milky Way appears as a bright band across the night sky because we are looking at the galaxy's plane side-on. But instead of looking across our galaxy's plane, we are looking across the comet's plane around the sun, according to Universe Today.  

Other notable comets that have been observed with an anti-tail include Comet Kohoutek in 1973, Comet Hale–Bopp in 1997 and Comet PanSTARRS in 2013.

This is not the first time that the green comet's tails have made headlines. On Jan. 12, the green comet was clearly visible in the night sky as it reached its perihelion, or closest point to the sun, which caused its small atmosphere, or coma, to glow brighter than normal. On Jan. 17, one of the comet's tails briefly separated mid-stream as it was blasted by extreme solar winds from a coronal mass ejection. 

If you’ve missed the comet so far, don't worry; it will become visible to the naked eye again in late January as it approaches its closest point to Earth on Feb. 1. Experts calculate that the last time the comet flew this close to Earth was around 50,000 years ago, when Homo sapiens were still sharing the planet with Neanderthals. 

Rainbows are colorful arches that stretch high into the sky, and they end somewhere in the distance (where the fabled pot of gold can be found), right?

Wrong.

Rainbows are actually not arches. They form as full circles when sunlight passes through raindrops at just the right angle. However, only part of the circle — the arch — is visible to the observer on the ground. Earth's surface blocks the rest of the light — and, therefore, the rest of the halo — which is why it appears as a rainbow. 

How much of the halo is visible depends on where the observer is standing and how much of the surface is in the way, said Michael Kavulich, a research scientist with the National Center for Atmospheric Research in Boulder, Colorado, and an expert on rainbows and why we see them as we do. It depends on refraction — how light is bent when it hits a raindrop — and reflection, which is light bouncing back. To understand why rainbows are really halos, you need to know how they form. 

"Most light entering a spherical raindrop ends up getting refracted at nearly the same angle, and if it also reflects once off the back of the raindrop this angle ends up being around 40-42 degrees from the direction the light is coming from," Kavulich told Live Science in an email. 

Related: Why does rain smell so good?

Yes, raindrops are actually spherical, not teardrop-shaped. According to the National Oceanic and Atmospheric Administration, light starts to bend, or refract, when it enters a raindrop because water is denser than air. The light continues to travel until it reaches the back of the raindrop. This is the phase where light bounces off the back. Now on its way out of the raindrop, the light refracts one more time and then separates into its iconic colors. 

Because raindrops are spherical, they reflect light in a cone shape. And what is at the end of the cone? That's right: a circle. So, while the pot of gold at the end of a rainbow may be a myth, a rainbow is still the end of something.

An observer's ability to see a rainbow depends on where they are standing in relation to the sun. What becomes visible is the light refracted and reflected at a certain angle — as Kavulich mentioned, about 40 degrees from that light's source — that hits the eye directly. For this to happen, the shadow of the observer's head has to be positioned exactly opposite from the sun (without the obstruction of clouds) so it can be in the middle of the circle, even if the entire circle is not visible. This is how they can see light refracted and reflected through the raindrops right in front of them. 

"Because of this, if you move, the rainbow does too, always staying in the same spot in the sky relative to the sun," Kavulich said. "You can only see it change if you look over a long period of time, as the sun rises or sets across the sky."

So why do we see colors in the classic ROYGBIV order? It's all about wavelengths of light. Kavulich explained that because red light has the longest visible wavelength, it is refracted the least, so it ends up at the top. Violet is at the bottom because it has the shortest wavelengths, which are refracted the most.

So, given that rainbows aren't actually arches, is there any way to see an entire rainbow in circular form? An airplane window is probably your best bet, though all or most of the circle is often visible from skyscrapers. There is sometimes a clear view from other high elevations such as mountains. Even then, too much is usually in the way. 

If you have no luck from those locations, you can try Kavulich's method of creating a circular rainbow with a garden hose. 

"You just need sunlight to be able to hit raindrops that you can see," he said. "With the right placement, I was able to see the whole circle at once."