Mysterious comet 31/ATLAS has just done something which looks like ‘controlled manouevering’, according to the scientist who made headlines claiming it could be an alien spacecraft.
The interstellar space rock was spotted in July, and is expected to pass back out of our solar system and into outer space… Unless there’s someone at the controls who might have other ideas?
Before you start panic buying toilet paper, we should point out that his theories are not widely accepted by other space researchers.
In fact, they’ve been made ‘to the annoyance of a lot of people who actually work on comets’, astrophysicist Dr Mark Norris told Metro.
But they are nevertheless making headlines, because Dr Avi Loeb, a controversial Harvard astrophysicist, has claimed the latest images could show it deployed ‘braking thrust’ to intentionally slow down.
A ‘black swan’ event?
While the idea of this comet being an alien spacecraft is far-fetched, Dr Loeb says we shouldn’t discount the possibility of a ‘black swan’ even, when something extremely unlikely with a severe impact happens, defying past observations and predictions.
Like, say, 31/ATLAS being a ‘Trojan Horse’ sent to our solar system from another civilisation for nefarious purposes.
Dr Loeb has been following its path, and previously speculated that it might do something unexpected right around now, when it is hidden behind the Sun.
It’s not the first time he has theorised an alien origin of a comet. There have only been three comets identified as coming from outside our solar system, and Dr Loeb also thought the first one, Oumuamu, showed signs of being ‘a thin craft pushed by the reflection of sunlight’ when it was found in 2017.
Lancaster lecturer Dr Norris said it is clear Oumuamu was not a spaceship, and he has not seen any proof so far that 31/ATLAS is behaving abnormally either.
‘A 30–40% likelihood that 3I/ATLAS does not have a fully natural origin’?
In a blog post earlier this month, Dr Loeb said he put the chance of the comet not being ‘fully natural’ at 30 to 40%.
He later updated his blog to say that latest photographs suggest 31/ATLAS’s tail of melting ice and rock began to point away from the Sun in September, instead of towards it as it had done in July and August.
In a blog post, Dr Loeb wrote: ‘My colleague, Adam Hibberd, pointed out that if the object is an alien spacecraft slowing down, and the anti-tail is braking thrust, then this change from anti-tail to tail would be entirely expected near perihelion [the point in orbit closest to the Sun].
‘In that case, the transition would constitute a technosignature in the form of an unexpected phenomenon indicative of controlled maneuvering, possibly with the intention of achieving a bound heliocentric orbot between Mars’s and Jupiter’s orbits.’
‘A fairly rare thing in comets’
This made headlines, but Dr Norris told Metro there are far more pedestrian explanations.
He acknowledged that it is rare for a comet to have a tail pointing towards the sun, ‘but it is seen in solar system comets occasionally. You have to have the right mixture of, things like how fast the comet’s spinning, the material the comet’s made of, and the size of the dust grains that are being emitted.’
He said that it can happen when a comet is very heavy and dusty. The front of the comet is the hottest, as it is the closest to the Sun, so this is where most particles are ejected.
Normally, the pressure of sunlight pushes the tail back behind the comet, but if the particles are heavy enough, this may not happen. ‘As you get closer and closer, the solar emission or the flux from the sun increases until eventually that tail starts to get pushed back and joins the rest of the tail.’
Dr Norris said: ‘So the fact that it has an anti-tail is not shocking. [Dr Loeb] has even written a paper that as far as I’m I’m aware, correctly explains why it happens and it has nothing to do in his explanation with aliens.
‘So why he lists it as a as proof of being aliens? You’d have to ask the guy.’
What about the way it’s moving?
Dr Norris added that the comet didn’t look like it was ‘braking’ in any case, as it was ‘speeding up because the gravity of the sun is pulling it closer’, and it was in full view rather than doing something where it was harder to observe.
One other ‘slightly unusual thing’ about it is that it has not shown any signs of ‘non-gravitational accelaration’ yet, and is moving exactly as it would be predicted to.
When a comet is pushing out a lot of gas, it tends to give it some thrust which changes its orbit slightly.
![[Image description: Three-panel infrared image of comet 3I/ATLAS taken by Webb on 6 August 2025. The left panel shows the overall infrared image with a bright white core fading to red, orange, and blue. The centre and right panels show flux maps highlighting CO? at 4.3 ?m and H?O at 2.7 ?m, respectively, with insets showing spectral line profiles confirming molecular signatures.] CREDIT NASA, ESA, CSA, M. Cordiner (NASA-GSFC)](https://metro.co.uk/wp-content/uploads/2025/10/SEI_268703048-13f3.jpg?quality=90&strip=all&w=646)
NASA, ESA, CSA, M. Cordiner)
But if it’s a very heavy comet body, it takes a lot of thrust to push it out of the way, which is probably the reason this hasn’t been detected, Dr Norris said.
‘That’s not particularly shocking,’ he added. ‘It’s interesting, but it’s not like proof of anything. It’s normal.’
Campaign to track 31/ATLAS
The International Asteroid Warning Network has started tracking the path of the comet, something that Dr Loeb said could be evidence that it is seen as a threat.
But Dr Norris was again sceptical, saying it was more likely they were doing so for training and scientific purposes: ‘Nobody would be very happy if we built a system to track hazardous asteroids, and it doesn’t do anything until the one time we need it to.’
He thinks the really exciting thing about these interstellar objects is that one day we may be able to intercept one of them, and physically see what another star system is made from, and how typical ours is.
Given that 31/ATLAS could be from a star system which formed billions of years before our own, when the galaxy had seen fewer stars living and dying, we would expect its chemical composition to be different to rocks in our own solar system, and it could behave differently as a result.
Where is 3I/Atlas now?
It’s not visible right now because it’s behind the Sun, and too bright for telescopes to see, but we will get another glimpse from November 2 when the European Space Agency’s JUICE spacecraft trains instruments on it, on its way to studying Jupiter.
According to Nasa, it will reach perihelion, its closest point to the Sun, around October 30, when it will be just inside the orbit of Mars.
It will reappear on the other side of the Sun by early December, when we should be able to see it again from Earth, and will pass reasonably close to Jupiter, but never within the orbit of Earth
Dr Norris said it will be visible until next year, and then will head out of sight towards the far edges of the solar system, then out of it completely within the next decade, and it will ‘continue out in the deep space for potentially millions more years’.
Can I see it in the sky?
If you have a reasonable amateur telescope.
Towards the end of November, it will be visible again in the early morning around 6am, just before the sun rises.
As time goes on, its separation with the sun will get bigger and bigger, so it will become visible earlier and earlier in the night.
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