Mystery discovery in space is most likely the 'oldest comet ever seen', say researchers
The "water ice-rich" visitor, which has been given the name 3I/ATLAS, is the first object to reach us from a completely different region of our galaxy, researchers have said.
Just two other objects have entered our solar system from elsewhere.
Unlike its predecessors, 3I/ATLAS seems to be travelling on a steep path that suggests it came from the Milky Way's "thick disk", an area of ancient stars that orbits above and below the thin plane where most stars reside.
University of Oxford astronomer Matthew Hopkins explained: "All non-interstellar comets such as Halley's Comet formed with our solar system, so are up to 4.5 billion years old.
"But interstellar visitors have the potential to be far older, and of those known about so far our statistical method suggests that 3I/ATLAS is very likely to be the oldest comet we have ever seen."
3I/ATLAS could be about three billion years older than our solar system.
It was first spotted on 1 July 2025 by the ATLAS survey telescope in Chile, when it was roughly 670 million kilometres from the sun. Earth is 149 million km away from the sun.
Professor Chris Lintott, the co-author of the study, said: "This is an object from a part of the galaxy we've never seen up close before.
"We think there's a two-thirds chance this comet is older than the solar system, and that it's been drifting through interstellar space ever since."
Read more from Sky News:
As 3I/ATLAS gets closer to the sun, sunlight will heat its surface and trigger the outgassing of vapour dust that creates a comet's glowing tail.
Members of the public could be able to catch a glimpse of 3I/ATLAS in the coming months, as researchers say it should be visible through reasonably-sized amateur telescopes in late 2025 and early 2026.
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WIRED
4 hours ago
- WIRED
Everything We Know About the Interstellar Object 3I/ATLAS
Jul 13, 2025 5:00 AM A team of astronomers recently discovered the traveling space object, just the third of its kind to pass through our solar system. NASA's projection of the trajectory of 3I/ATLAS, which is expected to pass between the orbits of Earth and Mars and make its closest approach to the Sun in October. ILLUSTRATION: NASA/JPL-CALTECH On July 2, NASA revealed the existence of 3I/ATLAS, only the third ever interstellar object observed in the universe. These are objects that exist in interstellar space—the areas between stars—and which are not gravitationally bound to any star. The two other interstellar objects discovered to date are the comets 1I/ʻOumuamua and 2I/Borisov. 3I/ATLAS was discovered on July 1, when its existence was reported by a telescope at Rio Hurtado in Chile, operated by the Asteroid Terrestrial Impact Alert System. Known commonly as ATLAS, this is a NASA-funded system developed and operated by the University of Hawaii to detect asteroids that could potentially hit Earth. It uses four telescopes—two in Hawaii, one in Chile, and one in South Africa—to automatically scan the entire sky several times each night to monitor celestial movements. An illustration of 1I/ʻOumuamua, which was the first ever interstellar object discovered in October 2017. It is thought to be up to 400 meters long and cigar-shaped. Illustration: ESA/Hubble, NASA, ESO, M. Kornmesser An image of 2I/Borisov, the second interstellar object discovered in August 2019. It is thought to be about 975 meters in diameter and moving at 177,000 km/h. PHOTOGRAPH: NASA/ESA/D. JEWITT (UCLA) Archived data collected in the preceding weeks by ATLAS' three other telescopes, as well as by the Zwicky Sky Facility at the Palomar Observatory, operated by the California Institute of Technology, confirmed the discovery. Additional observations of 3I/ATLAS were then made by numerous telescopes around the world, gradually revealing more details about it. Observations of 3I/ATLAS taken by the ATLAS telescope in Chile. Photograph: ATLAS/University of Hawaii/NASA 3I/ATLAS is estimated to be, at most, about 20 kilometers in size. It is currently located about 670 million kilometers from the sun and is approaching our star from the direction of Sagittarius at a speed of about 61 km per second. Its speed is expected to increase as it approaches the sun. When astronomers studied its orbit, they found that 3I/ATLAS was moving too fast to be bound by the sun's gravity and so will head straight through the solar system and into interstellar space, never to be seen again. An animation of 3I/ATLAS created using observations made by the ATLAS telescope at Rio Ultado in Chile. Video: ATLAS/UNIVERSITY OF HAWAII/NASA Generally, celestial bodies are named after their discoverers, but in the case of 3I/ATLAS, it was named after the ATLAS research team. The 'I' stands for 'interstellar,' indicating that the object came from outside the solar system; the '3' was added to the name because it is the third interstellar object discovered. The object was was uncovered because ATLAS initially identified it as something that might be on a possible collision path with Earth, but NASA says there is no risk of the object hitting our planet. Even when 3I/ATLAS is closest to Earth, it will be about 240 million kilometers away. An animation of 3I/ATLAS observations made on July 2 by astronomers at the Near Earth Object Coordination Center, a division of the Planetary Defence Office of the European Space Agency. Video: ESA/LAS CUMBRES OBSERVATORY 3I/ATLAS will be visible using ground-based telescopes until September. It will then enter the inner orbit of Mars in late October and will be hidden in the sun's shadow when it passes our star at its closest point, making it impossible to observe from Earth. However, it will reappear from the sun's shadow in early December and become visible again. 3I/ATLAS is an active comet, which means that as it gets close to the sun and heats up, the ice in its nucleus could sublimate and form a nebula-like cloud of gas and dust called a coma—otherwise known as a tail. Because 3I/ATLAS is an object that came from outside the solar system, it may provide valuable data about objects that exist in the further reaches of space. For this reason, astronomers around the world are now paying close attention to it. This story originally appeared on WIRED Japan and has been translated from Japanese.
Yahoo
a day ago
- Yahoo
An alien comet is now passing through our solar system. Here's what we know
Telescopes around the world are now tracking a new visitor to our celestial neighborhood. Streaking through at a speed and trajectory that not even the Sun's immense gravity can capture, we will only have a short time — perhaps until the end of 2025 or early 2026 — to learn everything we can from alien comet 3I/ATLAS. On July 1, 2025, the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope, located in northern Chile, spotted a new object just inside the orbit of Jupiter. ATLAS scans the sky every night looking for any new comets or asteroids, with specific interest in anything that could be on a collision course with Earth. However, this new object, initially named A11pl3Z, caught astronomers' attention for a completely different reason. Its trajectory wouldn't bring it anywhere near Earth. In fact, the closest it will come to us is just inside the orbit of Mars, at a distance of around 240 million kilometers away. For context, that's 90 million kilometres farther than the distance between the Earth and the Sun! This diagram shows the hyperbolic trajectory of interstellar comet 3I/ATLAS as it passes through the inner solar system. It will make its closest approach to the Sun, just inside the orbit of Mars, in October. (NASA/JPL-Caltech) No, the remarkable thing about A11pl3Z's path wasn't how close it would come to us. Instead, it was where that path traced back to! Newly named Comet 3I/ATLAS is now the third interstellar object we've spotted travelling through our solar system! The first interstellar object discovered, 1I/'Oumuamua in October 2017, was only detected after it passed around the Sun and was on its way back out into the galaxy. Analysis of its trajectory showed that it dove into the inner solar system from 'above', at a very steep angle, passed within the orbit of Mercury, and then slingshotted around the Sun to depart in a completely different direction. There is still some debate about exactly what 'Oumuamua (the Hawaiian word for 'scout') actually was. Observations revealed that it was likely dark red in colour, around 100-200 metres wide, and that it was either shaped like a cigar or a skipping stone, as it tumbled end-over-end passing through the solar system. It wasn't dense enough to be an asteroid, but it didn't behave like a comet, either. To throw some extra mystery into the event, as it departed, it even exhibited a small acceleration that couldn't be easily explained! The most likely answer is that 'Oumuamua was an ancient comet that had lost nearly all of its ice while journeying through the galaxy. However, we still don't know for sure. The paths of 'Oumuamua and Borisov through the inner solar system. (Image courtesy Tony873004/Wikimedia Commons (CC BY-SA 4.0)) The second object, 2I/Borisov in August 2019, also came from 'above' the solar system, although along a different trajectory than 'Oumuamua. Detected on its way in, astronomers watched it pass just outside the orbit of Mars before continuing on its way, only slightly deviating from its original path. Borisov was far less mysterious, as it exhibited all the characteristics we come to expect from comets. It was on the small side, at only around 500 metres across, but it developed a large coma surrounding the nucleus, and it had a wide, puffy tail as it passed by the orbit of Mars. Borisov's speed, trajectory, and odd chemical composition were the only aspects of the object that really set it apart from 'home grown' comets. This new interstellar object is quite different from the previous two. 3I/ATLAS is most certainly a comet, like 2I/Borisov. Currently just within the orbit of Jupiter, it is already being heated enough by the Sun's rays that a coma of gases has developed around the nucleus, and it has a short tail as well. A stacked image of several observations by the ESO's Very Large Telescope is shown here, to augment the brightness of comet 3I ATLAS and bring out more of its details. The solid nucleus of the comet is located within the bright region on the left side of the 'smudge', however it is currently obscured by the gas, ice, and dust of the comet's coma. (ESO/O. Hainaut) However, that is where the similarities (at least so far) end. From the comet's brightness, astronomers estimate that 3I/ATLAS's nucleus measures anywhere from 10-20 kilometres across. That makes it the largest interstellar object seen so far — at least 100 times the size of 'Oumuamua and 20 times bigger than Borisov. It is also the fastest of the three, travelling at nearly 60 kilometres per second, or 216,000 kph, compared to around 32 km/s for Borisov and 26 km/s for 'Oumuamua. Eight observations of comet 3I/ATLAS are shown here (circled), taken by the ESO's Very Large Telescope over the course of about 13 minutes on the night of July 3, 2025, revealing the movement of the comet against the background stars. (ESO/O. Hainaut) 1I/'Oumuamua and 2I/Borisov both approached us at very steep angles, entering the system from the general direction that the Sun is travelling through the galaxy. 3I/ATLAS, on the other hand, arrived from the direction of the galactic core, and is passing through the solar system at a much more shallow angle, almost perfectly in line with the ecliptic — the disk that the planets orbit along. Using a computer model based on data collected by the ESA's Gaia telescope, a team of researchers led by Matthew Hopkins of the University of Oxford has proposed that, based on its speed and trajectory, 3I/ATLAS could originate from one of the stars in the Milky Way's thick disk. This map of the Milky Way galaxy was compiled using data from the Gaia mission. The bright region that spans across the centre of the image is the galactic 'thin disk', while the more diffuse regions above and below that are known as the 'thick disk'. (ESA/Gaia/DPAC; CC BY-SA 3.0 IGO. Acknowledgement: A. Moitinho.) Based on what Gaia revealed about the stars in that region of the galaxy, this comet may have been ejected from its home star system long before our Sun even formed! "All non-interstellar comets such as Halley's comet formed with our solar system, so are up to 4.5 billion years old," Hopkins told the Royal Astronomical Society. "But interstellar visitors have the potential to be far older, and of those known about so far our statistical method suggests that 3I/ATLAS is very likely to be the oldest comet we have ever seen." Right now, with the comet still out near the orbit of Jupiter, it can only be seen with the strongest telescopes we have. This will get better over the next couple of months, though. Throughout July, August, and into September, the comet will grow brighter in our skies as it rises earlier and earlier, and thus tracks farther west each night. It will likely remain too faint to spot during that time. Interstellar comet 3I/ATLAS traces a path across the constellations Ophiuchus, Scorpius, and Libra, between July and September 2025, as shown by the orange line. The comet is now far too dim to see with anything less than an observatory telescope. By the time it reaches the constellation Libra, it might be visible to anyone with a quality backyard telescope. (Stellarium) In October, the comet will reach its closest point to the Sun. Unfortunately, it will be on the opposite side of the Sun from Earth. While it's blocked from sight here, it will be passing reasonably close to Mars. NASA and ESA orbiters could swing around and snap pictures of it as it flies past, providing us with closer views when it reaches its brightest near perihelion. 3I/ATLAS should reappear in the eastern predawn sky by November. When it does, this is when it should be bright enough — at magnitude 14 or so — for quality backyard telescopes to pick it up. Even with all of that said, comets are notoriously unpredictable. So, we can't be absolutely sure how 3I/ATLAS will respond as the Sun's rays heat it up. It is likely that it will follow the predictions and remain fairly dim in our skies. However, could there be a chance, however slim, that it will brighten much more significantly, giving us a spectacular show as it passes through and heads back out into interstellar space? Only time will tell. Click here to view the video
Forbes
2 days ago
- Forbes
3I/Atlas Isn't The First Interstellar Object To Visit Our Solar System
An interstellar object – a comet from a distant star system – is passing through the space between Jupiter and Mars, and according to a recent study, Comet 3I/Atlas may be 3 billion years older than our Solar System. CERRO PACHON, CHILE - JUNE 08: (——EDITORIAL USE ONLY - MANDATORY CREDIT - 'OBSERVATORIO VERA C. ... More RUBIN / HANDOUT' - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS——) The night sky dazzles above Rubin Observatory in this image in Cerro Pachon, Chile on June 08, 2025. Beginning in late 2025, Rubin Observatory's decade-long Legacy Survey of Space and Time (LSST) will generate an ultra-wide, ultra-high-definition time-lapse record of the Universe at Observatorio Vera C. Rubin, in Cerro Pachon, Chile. (Photo by OBSERVATORIO VERA C. RUBIN/ HANDOUT/Anadolu via Getty Images) Comet 3I/Atlas appears to hail from somewhere toward the center of the Milky Way (which makes sense, because most of the galaxy is 'toward the middle' from Earth). And according to astronomer Matthew Hopkins and his colleagues, the comet entered our Solar System at a steep angle, which suggests that it came from a region of the galaxy called the 'thick disk.' Most of the stars, gas, and dust that make up our galaxy orbit around the center in the same plane, a spiral-armed disk about 400 light years deep. But about 10% of the Milky Way's stars (by mass) orbit in the 1000 light years 'above' and 'below' the thin disk, like the stellar bread on a galactic sandwich. The thick disk is home to older stars with simpler chemical makeup than our young Sun, and there's very little interstellar gas or dust drifting between them. In other words, interstellar comet 3I/Atlas didn't just come from an alien star system – it came from a cosmic neighborhood very different, and much older than, our own. "We think there's a two-thirds chance this comet is older than the Solar System, and that it's been drifting through interstellar space ever since," said astronomer Chris Lintott, a coauthor of the study, in a recent press release. But though Comet 3I/Atlas may be the oldest interstellar object we've ever seen, it's not the first – it may even be one of thousands. Interstellar Object 'Oumuamua: A Messenger From Afar, Arriving First This artist's illustration shows what 'Oumuamua might look like if we had been able to get a closer ... More look. Interstellar object 1I/'Oumuamua was 21 million miles from Earth and already on its way out of the system when astronomers first spotted it in October 2017. That meant we got just a fleeting glimpse of the long, thin, red-hued chunk of rock as it tumbled into the cosmic distance – just enough to stir up wild speculation about alien space probes, in fact. After 'Oumuamua swung past the Sun, it accelerated slightly. Astronomers watching the asteroid's progress calculated that the pull of the Sun's gravity couldn't have accounted for that burst of speed. 'Oumuamua moved more like a comet than an asteroid; as comets get closer to the Sun, their icy nucleus starts to evaporate, releasing plumes of gas into space – which in turn give the comet a push that can speed it up or change its course. But 'Oumuamua moved like a comet, it didn't look like one. All that erupting gas and dust usually forms a cloud, or coma, around the comet's nucleus, along with a tail pointing away from the Sun. Harvard University astrophysicist Avi Loeb proposed that 'Oumuamua was actually a thin solar sail (a sail designed to catch solar radiation instead of wind), which had caught the solar wind and used it to accelerate. Other astronomers pointed out that the idea made no sense, because 'Oumuamua was tumbling as it passed through the Solar System, and a tumbling solar sail wouldn't have been very effective at all. It turned out that, according to a 2023 study, 'Oumuamua was really a comet all along – just a weird one. As it flew through interstellar space, cosmic rays had broken apart about a third of the water molecules trapped inside 'Oumuamua, creating a lot of loose hydrogen molecules. When 'Oumuamua approached the Sun and started venting gas, the hydrogen was too light to drag any dust along with it as it erupted, so the comet's coma and tail were invisible but could explain the bizarre acceleration. Interstellar Object Borisov: A Rogue Comet From A Dim Red Star The Hubble Space Telescope captured this image of Borisov when it was about 260 million miles away. Another piece of a distant star system, a rogue comet probably born around a red dwarf star, swept through our Solar System in late 2019, streaming a tail of gas and dust 100,000 miles long. (The comet itself, 2I/Borisov, was only about a mile wide when astronomers first spotted it.) 'We reasoned that Borisov is likely a representative of the star system it comes from,' Auburn University astronomer Dennis Bodewits said in a 2020 press release from NASA. In other words, 2I/Borisov's chemical makeup could offer some clues about the alien star it once orbited. The comet contained a surprising amount of carbon monoxide ice (some comets in our Solar System contain carbon monoxide ice, too, but not nearly as much of it), according to data from the Hubble Space Telescope and the National Radio Astronomy Observatory's Atacama Large Millimeter/submillimeter Array (ALMA), Because carbon monoxide needs much colder temperatures to freeze than water does, 2I/Borisov must have formed somewhere very cold: less than −337.04° Fahrenheit. That could point to the system of planets orbiting a type of small, dim star called a red dwarf. "Red dwarfs are much smaller and dimmer than the Sun, so the planet-forming material around them would be colder than the building blocks of our solar system," explained NASA in its press release at the time. And the odds are in favor of the red dwarf idea, because these dim, cool-burning stars make up about 75% of the stars in our galaxy. On the other hand, the carbon monoxide ice could also point to someplace like the outskirts of a system like ours; at 3.7 billion miles away from the Sun, dwarf planet Pluto's surface temperature ranges from -375° to -400° Fahrenheit, and there is carbon monoxide ice on its surface. So it's possible that 2I/Borisov is actually a chunk of a dwarf exoplanet – another star's version of Pluto – which got knocked into space by a meteor impact. Or maybe 2I/Borisov was always just a mile-wide clump of ice and dust that coalesced in the chilly outer reaches of its star system. Either way, something must have boosted the comet to escape velocity, letting it slip the bonds of its star's gravity and travel through interstellar space. In our own Solar System, migrating gas giants probably boosted some of the comets of the Oort Cloud into their long, lopsided orbits, and they may also have kicked an entire planet out into interstellar space. The same process could have flung 2I/Borisov out of its own star system. Interstellar Object Atlas: The Oldest Comet Ever Seen This diagram shows Atlas's likely route through our Solar System. And now, for the third time in less than a decade, another comet from another distant star system is passing through. Like 2I/Borisov, 3I/Atlas is probably a comet. Telescopes here on Earth can't see 3I/Atlas in much detail yet, but what they can see suggests that it's surrounded by a haze of gas, some of which is streaming outward to form a short tail, which will get larger as the comet gets closer to the Sun. That means 3I/Atlas is probably made of more ice than rock. And if Hopkins and his colleagues are right about its origins, a lot of that ice should be water, rather than other ices like carbon monoxide, carbon dioxide, or methane. 'The gases that may be seen in the future as 3I is heated by the Sun will test our model,' said co-author University of Canterbury in New Zealand astronomer Michele Bannister, a co-author of the recent study, in a press release. Comet 3I/Atlas looks larger than either 1I/'Oumuamua or 2I/Borisov; Atlas is somewhere between 6.2 and 12.4 miles wide, while Borisov was about a mile wide. Cigar-shaped 'Oumuamua, the smallest of the three, was less than 3,000 feet long and less than 500 feet wide. And Atlas is also 'moving considerably faster than the other two extrasolar objects that we previously discovered,' according to University of Lancashire astronomer Mark Norris in comments to Agence France Presse. 'Oumuamua was zooming along at around 86,000 miles per hour when it passed the Sun, and Borizov whizzed past at 98,000 miles per hour. Meanwhile, astronomers have already clocked Atlas at around 137,000 miles per hour, and it will be moving even faster by the time it passes by the Sun in October 2025. Interstellar Objects Pass Through More Often Than We Thought Authorities and scientists attend a simultaneous conference with the United States, after the first ... More images of deep space captured by the Vera Rubin Observatory in Chile were revealed, in Santiago on June 23, 2025. The team behind the long-awaited Vera Rubin Observatory in Chile published their first images on June 23, 2025, revealing breathtaking views of star-forming regions as well as distant galaxies. More than two decades in the making, the giant telescope, funded by the US National Science Foundation and the US Department of Energy is perched at the summit of Cerro Pachon in central Chile, where dark skies and dry air provide ideal conditions for observing the cosmos. (Photo by Rodrigo ARANGUA / AFP) (Photo by RODRIGO ARANGUA/AFP via Getty Images) So why are astronomers suddenly so many interstellar objects wandering through our Solar System? It's not because we're the hot new travel destination for wandering space rocks, but because new telescopes – like Vera Rubin – make it possible to see smaller, dimmer, and more distant objects. The presence of interstellar objects in our Solar System isn't anything new, but our ability to spot them definitely is. 'Astronomers estimate that an interstellar object similar to 'Oumuamua passes through the inner solar system about once per year, but they are faint and hard to spot and have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS1 [which spotted 'Oumuamua], are powerful enough to have a chance to discover them,' explains NASA on its webpage for 'Oumuamua. And now that the Vera Rubin Observatory is up and running, astronomers like Norris are optimistic about spotting more interstellar objects passing through the Solar System on their way to (and from) parts unknown: maybe as many as several a year. Meanwhile, a 2022 study suggested that we may actually have a few million samples of other star systems orbiting our own Sun. If University of Edinburg astronomer and statistician Jorge Peñarrubia is right, our Sun may have trapped a few million passing interstellar objects in the outer reaches of our Solar system. Some of them are stuck permanently, while others may make a couple of laps around the Sun and slingshot off into interstellar space again. It's a fascinating reminder that our Solar System is part of a wider galaxy – and not as isolated from it as we tend to think. As John Noonan of the Lunar and Planetary Laboratory at the University of Arizona, Tucson, said in the same 2020 NASA press release,'With an interstellar comet passing through our own solar system, it's like we get a sample of a planet orbiting another star showing up in our own backyard.'
