A rare object visiting from outside our solar system is travelling so fast it won’t be captured by the Sun’s gravity and is set to carry on back out into deep space.
It’s fascinating, but some think Comet 31 Atlas is more than just a nice thing to look out for in the sky.
They are convinced it’s evidence of alien technology, perhaps a probe sent on reconnaissance to learn more about our neighbourhood of the universe.
This is a fringe theory, but there are some in the scientific community who haven’t dismissed it out of hand.
Most high profile of them is Dr Avi Loeb, director of Harvard University astrophysics department’s Institute for Theory & Computation.
After the comet was identified this summer, he told Metro we should be concerned by the possibility it represents alien tech coming to scope us out.
‘This situation is starkly different from detecting a radio signal from a civilization located thousands of light years away,’ he said, referring to the aim of the SETI project.
‘In that case, humanity has plenty of time to contemplate how to respond and or worry about a visit from the transmitting civilization. However, if an interstellar object is a functional device on a near Earth trajectory, then the visitor is already in our back yard and we have little time to respond.’
3I Atlas live tracking
The comet is such an unusal visitor that Nasa has set up a tracker for people to keep an eye on what its doing. It passed Mars on October 3, and is now on its way towards perihelion (its closest point to the Sun).
After this, it will approach Jupiter in March next year, before heading back out of our solar system.
Nasa itself has shut down speculation that it could represent a sinister threat from another world.
They said: ‘Comet 3I/ATLAS poses no threat to Earth, approaching no closer than about 1.8 astronomical units (about 170 million miles, or 270 million kilometers).’
They said observations suggested it was not wider than 3.5 miles across, and we can expect it to reach its closest point to the sun around October 30.
But Dr Loeb said that the fact it achieves perihelion on the opposite side of the Sun relative to Earth ‘could be intentional to avoid detailed observations from Earth-based telescopes when the object is brightest or when gadgets are sent to Earth from that hidden vantage point’.
![This is a Hubble Space telescope image of the interstellar comet 3I/ATLAS. Hubble photographed the comet on 21 July 21 2025, when the comet was 445 million kilometres from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Because Hubble was tracking the comet moving along a hyperbolic trajectory, the stationary background stars are streaked in the exposure. [Image description: At the center of the image is a comet that appears as a teardrop-shaped bluish cocoon of dust coming off the comet???s solid, icy nucleus and seen against a black background. The comet appears to be heading to the bottom left corner of the image. About a dozen short, light blue diagonal streaks are seen scattered across the image, which are from background stars that appeared to move during the exposure because the telescope was tracking the moving comet.]](https://metro.co.uk/wp-content/uploads/2025/10/SEI_268702875-15b4.jpg?quality=90&strip=all&w=646)
He added that would be ‘impractible for earthlings’ to land on the comet even at its closest approach, because it is simply going too fast, and at the opposite direction of motion to the Earth: ‘our best rockets reach at most a third of that speed,’ even if earlier detection might have made it possible to intercept.
He wrote a paper looking at the possibility that Comet 31 is ‘a functioning technological artifact’, pointing out that while he does not necessarily believe it himself, he thinks it is worth examining as a hypothesis.
‘The cat is out of the bag’
Despite believing the ‘most likely outcome will be that 3I/ATLAS is a completely natural interstellar object, probably a comet’, he believes we must also consider the alternative.
This is because the consequences ‘could potentially be dire for humanity, and would possibly require defensive measures to be undertaken (though these might prove futile).’
He claimed it was possible that the comet/space ship could carry out a maneuver ‘to send smaller objects that will arrive at Earth’, saying that we should set up an international alert system for objects like this, in case one is more than it seems.
![[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-c369.jpg?quality=90&strip=all&w=646)
‘“The cat is out of the bag,” as we revealed our technological status through radio broadcasts over the past century,’ he said. ‘As a result, we should be ready for the possibility of a visitor that detected them. It may come to save us or destroy us. We better be ready for both options and check whether all interstellar objects are rocks.’
Can Comet 31 be seen from the UK?
Not right now. It is passing too close to the Sun to observe, according to Nasa.
It will reappear on the other side of the Sun by early December 2025, allowing for renewed observations, but you’ll need a telescope, not just binoculars.
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