Fuzzy, Large, And Very Old: Everything We Know About Interstellar Comet 3I/ATLAS
The object was detected on 1 July 2025, and it made a big splash. Scientists rapidly discovered that it came from outside the Solar System – just the third known object to have done so. Astronomers thronged to study, track, and categorize it.
Thanks to their efforts, we now have a pretty detailed – but still evolving – profile of the unusual comet. Initial observations suggest that it is very different from the other two interstellar objects, 1I/'Oumuamua, which appeared in 2017, and 2I/Borisov, discovered in 2019.
Related: Astronomers Have Traced Our New Interstellar Comet's Origin, And It's a First
Here's what we know. Please note that all papers are, at time of writing, preprints that are awaiting peer review.
Trajectory
Ongoing observations of 3I/ATLAS have enabled astronomers to chart its future path through the Solar System. It was discovered when it was at a distance of 4.5 astronomical units from the Sun (one astronomical unit is the distance between Earth and the Sun). That placed it inside the orbit of Jupiter.
It's traveling at just under 60 kilometers (37 miles) per second, but that will speed up as the comet approaches the Sun. 1I/'Oumumua was traveling at 26 kilometers per second, and 2I/Borisov at 32.
The closest 3I/ATLAS will come to the Sun is around 1.36 astronomical units, inside the orbit of Mars, on 29 October 2025. Its closest approach to Earth will be in December 2025, when it will come to a distance of 1.8 astronomical units.
Origin
The speed and trajectory of 3I/ATLAS suggest that it comes from the thick disk of the Milky Way, the puffy region around the thin disk wherein just 15 percent of the galaxy's stellar mass resides. This part of the galaxy is relatively sparse, and most of the stars in it are very old.
Age
The comet's origin provides clues about its age. Since it seems to hail from a region of mostly elderly objects, it stands to reason that 3I/ATLAS is likewise quite venerable.
This is supported by a separate paper that has analyzed the speed and velocity of the comet to try to calculate its age. It is traveling much faster than the two previous interstellar objects, 1I/'Oumuamua and 2I/Borisov, suggesting that it is older than them too. Future observations will help narrow down the object's age, but this analysis places it somewhere between 3 and 11 billion years old.
The Universe is 13.8 billion years old, and the Sun is 4.6 billion. 3I/ATLAS is unlikely to be at the upper end of the age range, but it's still probably older than the Solar System.
"This is an object from a part of the galaxy we've never seen up close before," says astrophysicist Chris Lintott of the University of Oxford in the UK, co-author of one of the papers that has emerged. "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."
Appearance
We don't know much about the appearance of 3I/ATLAS yet, because it is very small and still quite far away, but initial observations suggest that it is quite large compared to 1I/'Oumuamua and 2I/Borisov – about 10 kilometers across, compared to up to 400 meters long (around 1,300 feet) for 1I/'Oumuamua and 975 meters for 2I/Borisov.
The spectrum of light reflected off the comet has been measured by a number of independent teams, all arriving at the same findings, suggesting that the object has either a complex mix of grain sizes, a different composition from those of Solar System comets, or a combo of both explanations.
New images taken with the Gemini North telescope reveal the comet's puffy coma, a sort of 'atmosphere' of dust and gas that surrounds the comet. As it draws closer to the Sun, scientists expect its activity to pick up, resulting in cometary outgassing.
"3I/ATLAS likely contains ices, especially below the surface, and those ices may start to activate as it nears the Sun," says astronomer Darryl Seligman of Michigan State University in the US. "But until we detect specific gas emissions, like H2O, CO or CO2, we can't say for sure what kinds of ice or how much there is."
What next?
Astronomers are going to continue keeping a close eye on 3I/ATLAS. Since it is so much larger than either of the previous two interstellar visitors, it presents a much better observation target, and its projected origin and age means it represents a rare opportunity to study parts of the galaxy in time and space that are usually out of reach.
Its appearance has another implication, too. It suggests that interstellar visitors are relatively common to the Solar System – which is all the more reason to be excited about the forthcoming ESA/JAXA Comet Interceptor mission, designed to visit comets and study them up close, currently slated for a 2029 launch.
Related News
Sold: Largest Mars Rock Exceeds Auction Expectations
One of 2025's Best Meteor Showers Is Upon Us: Here's How to Watch
Meteorite Discovery Could Fill Billion Year Gap in Moon History
Solve the daily Crossword
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Gizmodo
16 hours ago
- Gizmodo
Interstellar Visitor Zipping Through Our Solar System Could Be a Hostile Probe, Alien-Hyping Scientists Warn
There's a visitor in town, and its name is 3I/ATLAS. The presumed interstellar comet presents a rare opportunity for astronomers to study an object born a long time ago in a star system far, far away. But a new paper uploaded to the preprint arXiv server asks an intriguing question: Is the object actually alien technology? For Harvard astronomer and study co-author Abraham Loeb, this is not his first interstellar rodeo. In 2018, Loeb proposed that the interstellar object 'Oumuamua might be an alien probe. He's now back at it, along with co-authors Adam Hibberd and Adam Crowl from the UK's Initiative for Interstellar Studies, asking the same question about 3I/ATLAS. The team is essentially flagging 3I/ATLAS as a candidate for alien technology and, perhaps alarmingly, as something that might actually pose an existential threat to humanity. Sounds absolutely bonkers, but it's a topic worth exploring and not something to reflexively toss onto the garbage heap. From the moment it entered our view, 3I/ATLAS—the third interstellar object ever detected in our solar system—instantly became the biggest news in astronomy for the month, if not the year. Astronomers are using the rare opportunity to study the object in as much detail as possible using the best instruments available. A clear picture of the object is emerging, suggesting it's very likely an enormous, icy comet that's considerably older than our solar system; preliminary estimates suggest it's 0.74 miles long (1.2 kilometers) and dates back some 7 billion years. An Interstellar Comet Is Here, and Its Age Is Mind-Bending The interstellar interloper is zipping through our solar system at ludicrous speeds, clocking in at 37 miles (60 kilometers) per second. Its velocity is so extreme that it'll exit our solar system and disappear from our view later this year, escaping the gravitational influence of our Sun. Astronomers are therefore under a tight deadline to understand everything they possibly can about 3I/ATLAS—an object that originated in some faraway protoplanetary or planetary system. That said, astronomers have already made some great strides in sketching out the finer details of 3I/ATLAS, quickly churning out papers pertaining to the visitor's age, size, velocity, spin, and, most importantly, its origin, based on observational data. According to research released earlier this week, the object is a jumble of organic molecules, silicates, and carbon-based minerals, placing it in a similar compositional category as asteroids found between Mars and Jupiter. Based on current data—much of it from researchers working with the newly launched Vera C. Rubin Observatory—3I/ATLAS is expected to pass through the asteroid belt between Mars and Jupiter later this fall, reaching its closest point to the Sun in late October. Excitingly, the Sun's warmth should sublimate enough ice on the comet to brighten the coma and tail even further. Suffice it to say, astronomers' ongoing investigations into 3I/ATLAS largely confirm that it's a cometary castaway. Like other comets we've seen before, 3I/ATLAS likely emerged from natural processes and was banished to interstellar space by some gravitational interaction, such as a close encounter with a gigantic planet or a passing star. Importantly, and despite strange, unfounded claims made in the new Loeb paper, there's zero indication that 3I/ATLAS is anything but a natural object formed by natural processes. Yet that hasn't stopped Loeb and his colleagues from venturing beyond the existing evidence. What's more, they've violated Occam's razor—a central tenet of the scientific method. Scientists are told that the simplest explanation is often the best when tackling puzzling phenomena. In this case, the simplest explanation, given the existing evidence, is that 3I/ATLAS is a comet. Often, when astronomers detect something unusual or inexplicable in space, there's the urge to invoke extraterrestrial influence. The Many, Many Times Astronomers Mistook Mundane Phenomena for Aliens This seems to be the case here, but as we'll discuss next, these researchers are not wrong to be asking these sorts of questions. As Sara Webb, an astrophysicist at the Swinburne University of Technology, wrote in The Conversation, 'Objects like 3I/ATLAS remind us that space is vast, strange, and full of surprises. Most of them have natural explanations. But the strangest objects are worth a second look.' Loeb and his colleagues do bring up a salient point—that we need to be curious about this object and not simply assume that it is what we think it is. Moreover, the team's warning that this object, should it be an alien probe, poses a potential hostile threat to humanity is rooted in some fascinating—if not disturbing—philosophical arguments having to do with our failed search for signs of extraterrestrial intelligence. The first is the Fermi Paradox—the surprising observation that, despite our galaxy's immense size and extreme age, we have yet to see any signs of intelligent aliens. As Italian physicist Enrico Fermi famously asked in 1950, 'Where is everybody?' This conundrum, known as the Great Silence, is not so easy to brush aside, as virtually all proposed solutions fail to convincingly account for the conspicuous absence of a Milky Way filled with extraterrestrials and extraterrestrial technology. This has led a number of philosophers, astrobiologists, and science-fiction writers to propose some rather grim solutions to the Fermi Paradox, that is, solutions that point to a galaxy devoid of space-faring civilizations. Loeb's new paper invokes one of these solutions, an idea known as the Dark Forest hypothesis. The term is borrowed from sci-fi author Liu Cixin, who made note of this possibility in his The Three-Body Problem trilogy, specifically the 2008 novel The Dark Forest. In Liu's imagined universe, intelligent civilizations stay silent and hidden because any interaction with aliens could be fatal; since it's impossible to know another civilization's intentions, the safest move is to eliminate potential threats before they can act. Hence, a Dark Forest galaxy, in which advanced civilizations take the form of silent hunters. This general concept didn't start with Liu; sci-fi novelist and SETI expert David Brin has been ruminating over the possibility of killer alien probes since 1983. As Loeb and his colleagues argue in the new paper, 3I/ATLAS, should it be artificial, is likely to possess 'active intelligence.' If that's the case, the object might be friendly, evil, or possibly something in between, they write. If it's benign, we can relax, but it's the second possibility—that it's malign—that's cause for 'most concern.' That's because the Dark Forest resolution to the Fermi Paradox is the more likely scenario, 'as it would neatly explain the singular lack of success of the SETI initiative to-date,' according to the paper. In other words, the reason we have yet to encounter aliens is that they're stealthy hunters, and this interstellar visitor, should it be a probe, likely belongs to that class of civilizations. Which is obviously not good for us. This argument brings the Berserker probe concept to mind, an idea proposed by another science fiction writer, Fred Saberhagen. The concept is as simple as it is disturbing: the solution to the Fermi Paradox is that all intelligent life is wiped out by self-replicating machines—known as Von Neumann probes—that methodically sterilize the galaxy of intelligence. All this talk of interstellar probes may seem outlandish, but there are a few things worth considering. First, our galaxy, across its 13-billion-year history, has likely spawned numerous advanced civilizations, many of which were (or are) capable of launching probes on interstellar missions. Secondly, we ourselves have already launched three interstellar (or interstellar-bound) probes as a result of exploring our immediate environment: both Voyager probes and New Horizons. It's therefore not unreasonable to assume that interstellar probes of varying ages and technologies are zipping around the Milky Way. One day, we just might spot one of these alien artifacts passing through our neck of the celestial woods. Let's hope it's friendly.
Yahoo
17 hours ago
- Yahoo
Life might have come from outer space, scientist say
The seeds of life on Earth might have come from outer space – and might be widespread throughout the rest of the universe, scientist say. Researchers have found complex organic molecules in a disc around a 'protostar' in a major breakthrough. Those molecules are seen as the precursors to the building blocks of life, which go on to become sugars and amino acids that are then combined into the complex flora and fauna that surrounds us. Researchers have found such complex organic molecules in other places before. But the new findings fill in a previously mysterious missing link – one that could suggest that life is more abundant than we realise. When cold protostar becomes a young star, surrounded by a disc of dust and gas, it is a violent process that includes intense radiation and the hurling out of gas. Researchers had been concerned that the extreme nature of that process could 'reset' the chemical compounds available around a star, meaning that they would have to be formed in the discs that at the same time are making planets. But the new findings suggest that complex molecules can stick around through that process, meaning they will be inherited by the discs that follow. The findings are reported in a new study, 'A deep search for Complex Organic Molecules toward the protoplanetary disk of V883 Ori', published in the The Astrophysical Journal Letters.
Associated Press
17 hours ago
- Associated Press
Leaping sturgeon provide a show for nature lovers on Maine rivers
AUGUSTA, Maine (AP) — The Kennebec River in Maine's capital city of Augusta is known for its population of Atlantic and shortnose sturgeon. The fish sometimes leap completely from the water, as at least one did on Wednesday. The shortnose population on the river nearly doubled from about 5,100 in the late 1970s to more than 9,400 around 2000, and it has likely grown since, state biologists have said. The ancient fish have also shown signs of recovering elsewhere in Maine, such as the Saco River further south. Scientists have proposed a number of reasons why sturgeon jump out of the water, including regulating their swim bladder, communicating with other sturgeon, shedding parasites and avoiding predators. Shortnose sturgeon can weigh up to 60 pounds (27 kilograms), while Atlantic sturgeon can be much larger, with some weighing as much as 800 pounds (363 kilograms). The fish thrill nature lovers who are fortunate to catch their sudden leaps along Maine rivers. Catching a glimpse of them is often a matter of luck.
