Comet 3I/ATLAS Warning: Strange Wobble and Sunward Tail Spark Frenzy Over Alien Origins

Comet 3I/ATLAS is drawing unusual attention because it doesn't behave the way most comets do in photographs and time-series imaging. As it heads back out of the inner solar system, astronomers are analysing an odd sunward-pointing dust feature and shifting jet-like structures that appear to change position in a repeating pattern.

The most baffling feature is a prominent 'anti-tail'—a dust stream that appears to extend a million kilometres in the Sun's direction, rather than trailing behind as expected. While such features are rare, the strength and structure of this one have made the comet a top priority for scientists studying interstellar visitors.

A Tail Pointing the 'Wrong' Way

A typical comet develops a coma and tail when sunlight heats surface ice, releasing gas and dust. Radiation pressure and the solar wind then push fine material outward, so the main tail generally points away from the Sun. In images of 3I/ATLAS, observers reported a prominent 'anti-tail'.

Anti-tails are rare but not unheard of; they can occur when Earth's viewing angle lines up with a thin sheet of dust along the comet's orbit, making it look like the comet has a tail pointing the 'wrong' way.

What makes this case noteworthy is that the reported anti-tail appears strong and extended—estimated at roughly 1,000,000 km—and shows structure within it rather than a smooth, static streak.

Puzzling Jets and a 15-Hour Spin

Beyond the anti-tail itself, astronomers flagged intermittent jet-like features that don't stay fixed from night to night. Instead, the apparent jet direction shifts in a way consistent with a repeating motion, suggesting the nucleus may be rotating while an active region periodically vents material.

A reported observing campaign using the Two-metre Twin Telescope (TTT) at Teide Observatory in Tenerife tracked the comet over 37 nights. Based on a repeating shift—described as a precessional pattern with a period of 7 hours 45 minutes—researchers inferred a nucleus rotation of about 15 hours 30 minutes.

A Rare Interstellar Visitor

3I/ATLAS is reported as only the third confirmed interstellar object to visit our solar system, following the object 1I/'Oumuamua in 2017 and the comet 2I/Borisov in 2019. Each has expanded what researchers can test about small bodies formed outside our solar system.

Borisov looked comparatively 'comet-like;, while 'Oumuamua sparked debate because its shape and non-gravitational acceleration were hard to pin down with limited data. If 3I/ATLAS truly shows a structured anti-tail and measurable jet precession, it may provide one of the clearest rotational/activity case studies for an interstellar visitor to date.

Where It Goes Next—and Why This Matters

After its closest approach to the Sun, 3I/ATLAS made its closest approach to Earth on 19 December at roughly 270,000,000 km. It is now departing on a hyperbolic path that should take it out of the solar system for good.

That one-time pass is exactly why detailed measurements matter. Every interstellar object is a short-lived chance to compare 'foreign' small-body physics—dust behaviour, volatile release, nucleus rotation, and jet morphology—against the comets and asteroids we've studied up close at home.

Even if the anti-tail turns out to be largely geometric, the reported jet variability and inferred rotation still provide useful constraints for models of surface activity in an object that likely formed around another star.