Mystery in space: In December, the origin of comet 3I/ATLAS will be determined

The interstellar comet 3I/ATLAS has kept the scientific community on edge since its discovery in July 2025. It is the third interstellar visitor detected in our solar system, after 1I/‘Oumuamua and 2I/Borisov.

Its unusual behavior, combined with its estimated size of between 5 and 11 kilometers (3.1 and 6.8 miles) in diameter, has sparked various theories. The observations scheduled for December will be key to solving the mystery.

An “anti-tail” that puzzled astronomers

In its first months of observation, 3I/ATLAS displayed an elongated structure that pointed directly at the Sun. This “reverse tail” contradicts the typical behavior of a comet, whose trail should point away from the star.

Even the Perseverance rover managed to capture images of that trail from Mars, which increased global scientific interest.

Unexpected transformation on the way to the Sun

In September, the comet underwent a remarkable evolution. The Nordic Optical Telescope recorded the disappearance of the anti-tail and the formation of a conventional tail oriented to the east.

Astronomers David Jewitt and Jane Luu highlighted that CO₂ is the driver of this activity, a trait consistent with other comets.

A spacecraft disguised as a comet?

The renowned astrophysicist Avi Loeb suggested an alternative hypothesis: if that retraction of the anti-tail were a maneuver, it could be a technosignature. His colleague Adam Hibberd proposes that the trajectory would seek to establish a stable orbit around the Sun.

Most experts dismiss that idea. They state that the mass loss—about 2 million tons—is normal in bodies containing volatile compounds. The nucleus would be around 33 billion tons.

December will be the key month

The upcoming observations will determine whether 3I/ATLAS behaves like a rare but natural comet, or if it still hides anomalies that justify bolder theories.