The Manhattan-sized interstellar visitor hurtling through space has captured the imaginations of UFO watchers and baffled boffins for months as it approaches Earth
The anti-tail of a mysterious object hurtling towards Earth is larger than the distance to the Moon – sparking fears it is a jet from a technological thruster.
The interstellar visitor 3I/Atlas is due to reach its closest point to us this week as it zooms through space at a whopping 150,000mph. And Harvard boffin Avi Loeb believes the sunward speed of the material in the anti-tail must be at least 130 meters per second.
He said: “Whether this speed can be maintained by sublimated dust or gas from pockets of ice facing the solar wind and solar radiation pressure remains to be studied. The alternative is a jet from a technological thruster.”
Theoretical physicist Loeb said the latest images of the Manhattan-sized space rock show a prominent anti-tail that extends out to half a million kilometers away from the nucleus of 3i/Atlas towards the Sun.
He added: “This length is larger than the average distance to the Moon: 384,400 kilometers. An anti-tail of this size had never been observed before for a comet.”
The object, believed by most scientists believe to be a comet, arrived at a distance of about 270 million kilometers from Earth on Sunday.
By December 19, it will get to a distance of 268.9 million kilometers, its closest point to Earth. Loeb said: “The data collected by numerous observatories on Earth and in space will inform us in the coming weeks on the nature of 3I/ATLAS.”
The interstellar visitor’s anti-tail was first pictured in July as it approached the Sun. Most boffins think it’s a comet that has been travelling for billions of years and the “anti-tail” is ice melting from the speeding space rock.
But Loeb previously insisted the fact it it still visible as the object zooms away from the Sun adds to his fears it could be an “extraterrestrial artefact” about to make first contact.
And he previously raised fears its approach towards Earth may present the best chance for it to deviate from its course and make contact with humans if it is alien technology.
He wrote in his most recent blog post: “We do not have a good census of the population of interstellar objects, including any traffic of technological objects through the inner solar system.
“Our state-of-the-art survey telescopes can only detect reflection of sunlight from objects that are larger than 100-meters in diameter, roughly the size of a football field, within a distance comparable to the Earth-Sun separation.
“This diameter is an order of magnitude bigger than the largest spacecraft that humanity launched so far. Existing astronomical surveys would miss near-Earth objects that travel much faster than tens of kilometers per second, the typical speed of asteroids or comets.
“In order to assess whether an interstellar object is an outlier that deserves a high rank on the Loeb Classification Scale, we need to know the probability distribution functions for its properties.
“Our assessment will be more reliable as the sample of interstellar objects gets larger.
“The challenge is familiar for those who seek a partner from a small pool of dating candidates, as it is difficult to decide how exceptional any of the early dating candidates are until we sample a large number of them.
“Our interstellar dating pool might go beyond what Science Fiction writers imagine.”
Discovered on July 1, 2025, 3i/Atlas is the third known object from outside our solar system to be discovered hurtling through space.
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