The interstellar comet 3I/ATLAS has puzzled astronomers with behaviour inconsistent with known comet physics. Its unusual anti-tail, which remains sun-facing rather than typical comet behaviour, has cast doubt on the ability of current survey telescopes to detect the full range of interstellar objects passing through our Solar System.

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 continues to display a Sun-facing anti-tail, confirmed by Hubble, Gemini and XMM-Newton observations, with explanations involving ice fragments and trailing objects.