Is 3I/ATLAS an Alien Spaceship? The Rare Interstellar Object Explained
This year, we’re welcoming a rare guest in our skies – the interstellar comet 3I/ATLAS! It’s only the third interstellar object ever discovered, making it a once-in-a-lifetime visitor. But some argue we shouldn’t dismiss a wilder possibility: could it be an alien probe passing through our Solar System? Whatever you believe, you can follow its journey yourself. Track 3I/ATLAS in seconds with the free Sky Tonight app — your pocket guide to spotting cosmic visitors.
Contents
- What is 3I/ATLAS?
- Could 3I/ATLAS be an interstellar alien ship? Theory by the Harvard professor
- Comet 3I/ATLAS: official science position
- Frequently asked questions about the comet 3I/ATLAS
- Comet 3I/ATLAS: observing tips
- Comet 3I/ATLAS discovery
- Comet 3I/ATLAS: to sum up
What is 3I/ATLAS?
3I/ATLAS is a newly discovered interstellar object — a rare visitor from beyond our Solar System. It was first spotted on July 1, 2025, by the ATLAS survey telescope in Chile. The official view, supported by NASA, ESA, and most astronomers, is straightforward: 3I/ATLAS is a natural comet — the third interstellar object ever confirmed, after ‘Oumuamua and comet 2I/Borisov. But not everyone is convinced, and some argue that its unusual properties leave room for more exotic explanations.
Could 3I/ATLAS be an interstellar alien ship? Theory by the Harvard professor
Theoretical physicist and Harvard professor Avi Loeb stirred up the debate by suggesting we shouldn’t rule out the boldest possibility: that 3I/ATLAS might not be just a natural lump of ice and dust, but an artificial object controlled by aliens. Here’s what he pointed to.
3I/ATLAS is exceptionally big
When 3I/ATLAS was first spotted, it looked too bright for its distance. If all the light were just reflected sunlight, the object would have to be a whopping 20 kilometers across — far larger than expected for a random interstellar rock. Statistically, the odds of stumbling upon such a giant first were about 0.0001. Loeb argued this made the discovery suspicious.
3I/ATLAS doesn’t behave like a comet
When comets get closer to the Sun, they usually put on a show – long tails of gas and dust, plus clear chemical “fingerprints” in their spectra. But when Loeb raised his theory, 3I/ATLAS wasn’t showing either. Its spectrum lacked the telltale signs of gases like carbon dioxide or methane and instead revealed only a reddish reflection of sunlight. That red glow could be explained by dusty organics on the surface, but to Loeb it hinted at something less ordinary. With no cometary plume and no asteroid-like explanation either… what is it?
3I/ATLAS follows the suspiciously tidy trajectory
Random interstellar visitors usually barrel in from odd angles, cutting across the Solar System wherever gravity flings them. But 3I/ATLAS is gliding almost perfectly along the planetary plane — and not just anywhere, but passing close to Jupiter, Mars, and Venus along the way. To Loeb, that feels a little too neat to be a coincidence. This kind of alignment looks less like a random arrival and more like the sort of flyby route you’d plot if you wanted to survey the Solar System up close.
Also, skimming past massive planets could, in theory, allow for gravitational assists — the very same maneuver human spacecraft use to slingshot themselves deeper into space without burning extra fuel. So the question hangs in the air: is 3I/ATLAS just following the physics… or is the physics being used on purpose?
3I/ATLAS aims to hide from observers
As it glides through the Solar System, 3I/ATLAS will pass close to three Solar System planets — but carefully avoid Earth. At the end of October, it will slip behind the Sun, vanishing from our telescopes for weeks. Loeb points out that if the object were under intelligent control, this would be the perfect moment to perform a secret course correction — safely hidden from prying eyes on Earth. In his view, that’s exactly the kind of move a technological probe, aware of being watched, might make.
3I/ATLAS might be dangerous to Earth
As we mentioned before, disappearing behind the Sun could give 3I/ATLAS the chance to change its path without anyone noticing. And if that new trajectory were aimed at Earth, it wouldn’t be a friendly visit. In his scenario, such a move could mean a deliberate rendezvous with our planet — one with potentially hostile intent. He even suggested that humanity might have to consider ways of defending itself, though any technology advanced enough to cross the stars might render those defenses useless.
Though Loeb admitted in his blogpost that his spaceship scenario was more of an intellectual exercise than a firm conclusion, it certainly succeeded in sparking headlines and debate.
Comet 3I/ATLAS: official science position
Not everyone is buying Loeb’s “alien probe” angle. NASA, ESA, and the wider astronomy community are clear: the latest evidence overwhelmingly shows that 3I/ATLAS is a comet.
3I/ATLAS is not that big
While early math suggested a monster-sized body, Hubble imagery shows otherwise. Now, the nucleus is estimated at 0.6–5.6 km across – perfectly ordinary for a comet. Much of the early brightness was due to surrounding dust, not a giant rock.
3I/ATLAS behaves like a textbook comet
For most astronomers, the case is simple: 3I/ATLAS looks and acts just like a comet. It’s growing a coma and tail, spewing out dust and gas, and brightening as the Sun’s heat wakes it up. Observations with NASA’s SPHEREx telescope have even picked up a clear signature of carbon dioxide in its coma — a classic comet marker. As Tom Statler, NASA’s lead scientist for solar system small bodies, summed it up: “It looks like a comet. It does comet things.”
3I/ATLAS is no threat to Earth
The dramatic “alien ambush” idea makes for great science fiction, but astronomers emphasize that the real orbit of 3I/ATLAS is well understood. Careful calculations using data from ground-based telescopes and space observatories show that the comet will stay at least 270 million kilometers away from Earth — almost twice the distance between Earth and the Sun. Astronomers emphasize that 3I/ATLAS is behaving exactly like a natural comet, and the only invasion it is planning is of your telescope’s eyepiece.
So, is 3I/ATLAS really an alien spacecraft on a secret mission, or just a comet occasionally passing through our neighborhood? Most scientists are firmly in the second camp.
Frequently asked questions about the comet 3I/ATLAS
Why is comet 3I/ATLAS special?
To begin with, it’s a true interstellar object, meaning it didn’t form in our Solar System but came from another star system entirely. Such objects are incredibly rare, so each new one causes a stir. On top of that, early estimates suggest its core could be up to 5 kilometers across, making it one of the largest interstellar bodies we’ve ever spotted. And the best part is that this cosmic traveler will actually be visible in the sky this year.
Is comet 3I/ATLAS the only interstellar object found so far?
Nope! In fact, 3I/ATLAS is the third confirmed interstellar object to enter our Solar System. The very first was the oddly shaped object called ‘Oumuamua, discovered in 2017 — an elongated rock, which some thought looked like an alien spaceship. Then came 2I/Borisov in 2019, which behaved like a typical comet with a bright coma and tail.
How do we know that 3I/ATLAS is not from our Solar System?
Its unusual trajectory was the first big clue — it wasn’t closed, but had a hyperbolic shape, so astronomers suspected the comet wasn't local. Later, orbital calculations confirmed it: 3I/ATLAS is traveling at about 210,000 km/h, a speed typical of interstellar objects and far too high for something bound by the Sun’s gravity.
Will the comet 3I/ATLAS hit Earth?
No need to worry — comet 3I/ATLAS will pass through the inner part of our planetary system, but it will remain very far from Earth. Its closest approach to our planet will be about 1.8 AU — that’s roughly 270 million km, nearly twice the average Earth–Sun distance.
Is 3I/ATLAS for sure a comet? Can it be an alien spaceship?
Most likely, 3I/ATLAS is a comet. It has an icy nucleus, produces gas and dust, and grows a coma and tail — textbook comet behavior (you can check our special article about comets and see for yourself). We might have hoped for alien friends, but not this time.
People want to believe, which is why so many ordinary things get mistaken for UFOs: from balloons to human-made satellites in the night sky. To help you out, we’ve collected the most common mix-ups in our infographic. Don’t let yourself be fooled!
Comet 3I/ATLAS: observing tips
Want to catch a glimpse of a traveler from another star system? Comet 3I/ATLAS is passing through our cosmic neighborhood, and with the right timing and equipment, you can spot it for yourself. Below, we’ll walk you through how bright it will get, when and where to look, and how to avoid common pitfalls (like the glare of the Moon) to maximize your chances.
How bright will comet 3I/ATLAS get?
When it was first discovered, the comet was extremely dim, shining at about magnitude 17. By September 2025, it had brightened into the magnitude 12–14. Optimistic forecasts suggest that by late October, it could reach a magnitude of 12. If so, 3I/ATLAS would be the brightest interstellar object ever observed — but still too faint to see without a telescope. Even binoculars won’t quite cut it.
When and where to see comet 3I/ATLAS?
The orbit of comet 3I/ATLAS lies almost in the plane of the planets (inclination ≈5° to the ecliptic), which means it can be observed from both hemispheres.
- September 2025: The comet will shine in the evening sky as it drifts through the constellation Libra. From the Northern Hemisphere, it will appear low above the southwestern horizon after sunset, while in the Southern Hemisphere, it will climb higher into the sky.
- October 2025: The comet will slip too close to the Sun’s glare to be seen. Around mid-month, it will reach solar conjunction and vanish from view for several weeks. On October 29, 3I/ATLAS will reach its perihelion (closest point to the Sun) and begin migrating to the morning sky.
- Late November 2025: The comet will return to view, this time before dawn in the constellation Virgo, low above the eastern horizon. Its brightness is expected to hover around magnitude 12–13 (though forecasts may change), after which it will gradually start to fade.
- December 2025: 3I/ATLAS will move into the constellation Leo, still visible in the early morning hours. By then, however, its brightness will have dropped quickly to about magnitude 14 and fainter. As the year ends, the comet will drift away, leaving the Solar System behind.
Mind the Moon phase
The Moon is a powerful light source that can easily obscure faint objects in the night sky. If you want to increase your chances of spotting interstellar comet 3I/ATLAS, plan your observations around the New Moon, when the sky is darkest.
- During the comet’s visibility period, the New Moon falls on September 21, October 21, and November 19. The Full Moon will occur on October 7 and November 5, making it much harder to catch the comet, due to the glare of moonlight.
For more detailed information, see the Moon phase calendar on our website.
Where is comet 3I/ATLAS right now?
Until the beginning of October, the comet will be passing through the constellation Libra. You can use the free Sky Tonight app as a comet tracker to pinpoint its exact location in the sky:
- Launch the app and tap the magnifying glass icon at the bottom of the screen;
- Type “C/2025 N1” into the search bar, then tap the blue target icon — the comet will appear on the sky map.
- Point your device toward the sky and simply follow the white arrow on the screen until it guides you to comet 3I/ATLAS above your location.
Comet 3I/ATLAS discovery
The comet was discovered on July 1, 2025, by an automated telescope of the ATLAS project in Chile, which was created to search for potentially hazardous asteroids. In the images, the object appeared as a very faint 20th-magnitude star, located about 4.5 billion kilometers from the Sun. Already the next day, calculations showed that its trajectory was not closed and had a hyperbolic shape. This meant the body had arrived from beyond the Solar System. On July 2, the Minor Planet Center officially confirmed its interstellar status.
Initially, the object was thought to be an asteroid, but subsequent observations revealed signs of cometary activity, including a small coma and a short tail. Over the following weeks, its brightness increased slowly, and it became clear that this was a full-fledged comet.
Why is comet 3I/ATLAS named like that?
The comet actually has two official names: C/2025 N1 (ATLAS) and 3I/ATLAS. They may look like different objects, but both refer to the same comet — the names just highlight different aspects of it.
C/2025 N1 (ATLAS) is the comet’s provisional designation, following standard naming rules by the IAU:
- C/ — non-periodic comet.
- 2025 — the year of discovery.
- N1 — the first object discovered in the first half of July (the “N” period).
- ATLAS — the discovery project.
3I/ATLAS is the other designation, which also follows the IAU naming system, but emphasizes the comet’s interstellar nature:
- 3I shows it’s the third confirmed interstellar object (after 1I/‘Oumuamua and 2I/Borisov).
- ATLAS again refers to the discovery project.
So, C/2025 N1 (ATLAS) places the comet in the catalog of Solar System comets, while 3I/ATLAS emphasizes its unique status as an interstellar visitor. Both names are correct — they just tell the story from different angles.
Why are interstellar comets like 3I/ATLAS so rare?
Most comets we see in the night sky belong to the Solar System. They were born billions of years ago in distant regions such as the Oort Cloud or Kuiper Belt and follow long, elliptical orbits around the Sun. Sometimes planetary gravity tweaks their paths, but they remain bound to our star.
An interstellar comet, however, has a completely different story. It forms in another planetary system and then receives such a strong gravitational “kick” from planets or passing stars that it is ejected forever. From that moment, it drifts through the galaxy for millions or even billions of years, until by sheer chance it passes through the Solar System. That chance is vanishingly small — which is why only three interstellar objects have been identified so far, with 3I/ATLAS among them.
Why do astronomers pay so much attention to interstellar objects?
Interstellar visitors like 3I/ATLAS are priceless to science because they act as natural messengers from other star systems. Unlike local comets, which were born in our own Solar System, these objects formed around entirely different stars and then wandered across the galaxy for millions or even billions of years before reaching us.
Studying them lets astronomers compare how planets and comets form under different conditions. Observations of 3I/ATLAS show that its composition most certainly includes water and carbon dioxide – the same ingredients we see in many Solar System comets. This suggests that the recipe for building comets, and perhaps even the raw materials for planets, may be surprisingly similar across the galaxy.
Comet 3I/ATLAS: to sum up
Comet 3I/ATLAS (C/2025 N1) is only the third interstellar object ever spotted in our Solar System, after ‘Oumuamua and 2I/Borisov. It’s large — with a nucleus estimated at 0.6–5.6 km across — and fast, racing along at about 210,000 km/h. While it won’t become visible to the naked eye, telescopes should reveal it at around magnitude 12 in late November 2025. Don’t miss your chance to track a messenger from another star system! With the free Sky Tonight app, you can find comet 3I/ATLAS in seconds, plan your observing sessions, and follow its journey across the constellations.
