Overview
- 3I/ATLAS will make its closest approach on December 19 at roughly 270 million kilometers from Earth (about 1.8 AU), and NASA says it poses no threat.
- Reports citing the Minor Planet Center and NASA’s JPL describe a fivefold increase in green‑band brightness and a non‑gravitational acceleration whose cause remains unclear.
- Astronomers note that if outgassing were driving the push, a massive gas coma would be expected, yet preliminary imaging has not shown a commensurate cloud.
- A coordinated campaign will target the object with Hubble, the James Webb Space Telescope, TESS, Swift and SPHEREx, with NASA planning a post‑encounter data effort starting December 29.
- Early studies report unusual chemistry, including nickel vapor, water and novel compounds with a possibly large nucleus of up to ~20 km, findings that teams aim to verify during December observations.