3I/ATLAS continues to exhibit a relatively rare dust antitail.

As 3I/ATLAS moves away from the Sun, as expected, increasingly high-quality photographs of the object are beginning to arrive, revealing some previously hidden (or missing) details. The most remarkable of these is undoubtedly the anti-tail, oriented opposite to the main, normal tail.

It should be noted that anti-tails, although uncommon, are observed in ordinary comets and have an accepted scientific explanation, which, however, does not apply in this case. This explanation is that the comet, moving in its orbit, leaves behind a dust trail that is almost undetectable due to its thinness and faintness. However, if Earth passes through the comet's orbital plane, this tail becomes visible edge-on for a very short time, literally 1-2 days, causing it to dramatically increase in brightness. Sometimes this looks quite impressive—for example, the comet C/2023 A3 (Tsuchinshan–ATLAS)) once displayed such an antitail.

Why isn't this appropriate? Simply because we're not currently passing through the orbital plane of 3I/ATLAS (that won't happen until the first half of December), and also because the tail has clearly been observed for longer than 1-2 days. Apparently, it was present from the very beginning, immediately after its discovery, including before its passage behind the Sun, and is a long-lasting, and possibly permanent, feature of the body.

Leaving conspiracy theories aside and leaving this to the professionals, we'll say that science does have a boring natural explanation for this phenomenon, which (to be fair, very rarely) has already been observed in bodies recognized as simple comets, not alien spacecraft. For example, comet C/2014 UN271 (Bernardinelli–Bernstein) has a similar explanation. It suggests that, in addition to fine dust easily blown by the Sun into a huge tail trailing behind the comet, a slow release and accumulation of coarse dust can occur on the Sun-facing side. This coarse dust cannot be displaced by the pressure of sunlight and remains on the Sun-facing side, gradually forming a short but clearly visible structure. It's difficult to imagine this explanation satisfying proponents of the technological nature of 3I/ATLAS, especially given the rather limited number of such observations on other bodies, as well as the unusual stability of this structure on 3I/ATLAS. Nevertheless, natural examples of such observations do exist, allowing science to apply its most beloved and powerful tool—Occam's razor—without restraint, cutting down all its opponents.

The question of what will happen to this tail next is quite interesting, since, by and large, the question of its nature remains unresolved. We'll see if it changes in any way after 3I/ATLAS crosses Earth's orbital plane on December 9-10 and we begin observing the celestial body from the other side.