Overview
- SOHO’s SWAN instrument measured peak post‑perihelion water production of 3.17 × 10^29 molecules per second on November 6, followed by a steady drop to roughly 10–20 trillion molecules per second by early December.
- Hubble images from November and December show a prominent anti‑tail and a symmetric trio of evolving jets that researchers are analyzing as unusual but not dispositive of non‑natural origins.
- Breakthrough Listen used the Green Bank Telescope near closest approach in mid‑December and found no credible narrowband radio signals attributable to 3I/ATLAS.
- The radio search initially surfaced about 470,000 candidate events, all of which were eliminated after off‑source checks or identified as terrestrial interference, with similar null results reported by other teams.
- Hubble constraints place the nucleus between roughly 440 meters and 5.6 kilometers in diameter, implying an unusually large active fraction—possibly around 20%—if surface sublimation drives the observed outgassing.