Overview
- 3I/ATLAS reaches closest approach on December 19 on the far side of the Sun at about 270 million kilometers from Earth, a distance agencies say poses no risk.
- Recent Gemini/NOIRLab images document a shift from reddish to green, attributed to diatomic carbon (C2) emission in the coma following perihelion.
- ESA’s XMM-Newton detected low-energy X-rays on December 3 consistent with solar-wind charge exchange, complementing optical and infrared findings.
- The comet shows two distinct tails and rhythmic brightening about every 16.16 hours that NASA and ESA attribute to rotating jets of gas and dust.
- Observers will need telescopes to spot the roughly magnitude-10 object before dawn low in the southeast near Virgo and Leo, and it will depart the Solar System on a hyperbolic trajectory as the third confirmed interstellar visitor; reports of unusually high CH3OH and HCN from ALMA have been circulated but remain to be fully detailed.