Overview
- 3I/ATLAS reaches its closest approach to Earth on December 19 at roughly 270 million kilometers, a safely distant pass.
- High‑resolution Gemini North observations across 360–1,030 nm show the coma brighter and distinctly greener than pre‑perihelion images.
- The green emission is linked to short‑lived C2 in the coma, which typically does not extend into the tail due to rapid decay.
- Hubble imaged the comet on November 30 and ESA’s XMM‑Newton detected X‑rays from solar‑wind interactions, with continued observations planned for months.
- Astronomers are watching for possible delayed outbursts or fragmentation, and the IAWN is running an astrometry campaign through late January to refine the orbit.