Overview

• A draft study using 4,022 Minor Planet Center astrometric measurements from May 15 to September 23 reports no detectable non‑gravitational acceleration, implying a nucleus mass above roughly 33 billion tons and a diameter greater than about 5 km.
• Despite a CO2‑rich coma and Webb’s August 6 measurement of ~150 kg/s mass loss at ~440 m/s, the object’s trajectory remains consistent with gravity alone.
• NASA has confirmed 3I/ATLAS as an interstellar visitor, only the third known after 1I/ʻOumuamua and 2I/Borisov.
• Next observations include Mars Reconnaissance Orbiter’s HiRISE imaging on October 3 at ~30 km per pixel and a Juno flyby opportunity on March 16, 2026 to refine size and activity estimates.
• Researchers highlight that forthcoming surveys, notably the Vera C. Rubin Observatory’s LSST, are expected to boost interstellar object detections and place 3I/ATLAS in better statistical context, while any unconventional-origin ideas remain speculative.