Overview

• A study released September 24 reports no measurable non‑gravitational acceleration from May to September, implying a nucleus mass above 33 billion tons and a diameter exceeding roughly 5 kilometers.
• The inference combines dense astrometry compiled by the Minor Planet Center—4,022 observations from 227 observatories—with JWST measurements of gas and dust loss to set strict limits on recoil effects.
• Earlier this week, a solar coronal mass ejection was forecast to intersect 3I/ATLAS, an uncommon encounter whose effects are unclear, though past CME hits have briefly stripped comet tails.
• NASA classifies 3I/ATLAS as an interstellar comet and notes it poses no threat to Earth; it will slip behind the Sun in late October and is expected to reappear for observers in early December.
• The mass estimate is from a draft that has not yet been peer reviewed, and most researchers continue to treat the object as a natural active comet despite its unusual behavior and composition.