3I/ATLAS will soon be approaching Earth at its nearest to the only known planet with life teeming. On its closest flyby on December 19, 2025, all the observatories will be glued onto the exocomet to get a clearer view and settle once and for all the debate of its origin.
Since its discovery on July 01, 2025 by the Asteroid Terrestrial-Impact Last Alert System (ATLAS), the interstellar interloper has baffled the scientific community and stargazers alike, while social media users brew conspiracy conjectures.
The anomalous nature of the exocomet becomes even more bizarre with blurry and grainy portraits of the object, infamously captured by NASA, ESA, and other observatories. For no fault of their own, though. The internet doesn’t bother to delve into technicalities. They want Hollywood-grade space visuals every single time. Who is to blame?
Speaking of which, is the interstellar comet actually of an extraterrestrial intelligence origin, carrying perhaps more probes or even aliens? Highly unlikely, given its cometary behavior, but as Prof. Avi Loeb, the Harvard astrophysicist, explains here, a space probe may also depict similar behavior after traveling through space for a considerable period. Nonetheless, a typical textbook comet always depicts a tail and momentarily an anti-tail. However, 3I/ATLAS continues to show an anti-tail, which earlier was presumed to be several jets from the object.
Prof Loeb states that in the latest images (above) taken by Teerasak Thaluang on December 13, 2025 with a 0.26-meter telescope in Rayong, Thailand The rotational-gradient brightness map shows a prominent anti-tail, uncommon for comets, pointing in the direction of the Sun.
He continues
Whereas an anti-tail had been seen for solar system comets as a temporary perspective effect when the Earth crossed the comets’ orbital plane, this is clearly not the case with 3I/ATLAS. The anti-tail was apparent in the first Hubble Space Telescope image, taken on July 21, 2025, when 3I/ATLAS was approaching the Sun from a geocentric distance of 2.98 times the Earth-Sun separation (AU) and was also apparent in the second Hubble image taken on November 30, 2025, when 3I/ATLAS was receding away from the Sun at a distance of 1.91 AU from Earth.
Prof Loeb argues
The anti-tail of 3I/ATLAS is therefore not a perspective effect. It is a real physical jet, with a glow extending from 3I/ATLAS towards the Sun. Its nature is a mystery because gas and micrometer-dust particles are expected to be pushed away from the Sun by solar radiation pressure and the solar wind, creating the appearance of a tail—as routinely seen in solar-system comets.
He grills NASA in his next statement for evading any statement on the anti-tail
There was no mention of this mystery at the NASA press conference about 3I/ATLAS on November 19, 2025
In one of his three papers, Avi Loeb decodes the anti-tail of 3I/ATLAS, suspecting it carry
a swarm of objects that lag behind 3I/ATLAS because of its non-gravitational acceleration away from the Sun
See Also: EXCLUSIVE: Harvard Astrophysicist Avi Loeb On 3I/ATLAS, Aliens, Stranger Things & Indian Food
