In the spirit of the season, the interstellar comet 3I/ATLAS is changing color as it leaves the sun behind — shifting from a reddish tint to a faint green glow. That visible change signals the comet is reacting to solar heat and releasing new gases in space, giving scientists fresh clues about what it is made of and how it behaves.

Interstellar object 3I/ATLAS nears Earth with a bizarre 'anti-tail' and 14 anomalies. Is it a comet or alien tech?

Astronomers detect "wobbling high-latitude jet" in comet 3I/ATLAS, according to a preprint paper. A new mutation of flu strain A (H3N2) is driving an increase in influenza cases and hospitalizations. Bears in central Italy are evolving to become smaller and less aggressive after interacting with humans, study finds.

Discovered on July 1 by the NASA-funded ATLAS telescope in Chile, 3I/ATLAS is only the third confirmed visitor from another solar system, following 1I/'Oumuamua in 2017 and comet 2I/Borisov in 2019.

Comet 3I/ATLAS, an interstellar visitor, reaches its closest approach to Earth on Dec 19 at about 167 million miles - visible only with a strong telescope. Newsround speaks to an astrophysicist to find out all about it.