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New Images Show Interstellar Comet 3I/ATLAS Glowing Green With an Elusive Tail After Sun Swing

The object will pass Earth safely at about 270 million kilometres on December 19.

Overview

  • Post‑perihelion images taken November 5 by Lowell Observatory’s Qicheng Zhang show a bright blue‑green coma with no obvious dust tail, a view researchers say is consistent with diatomic carbon emission and a tail aligned nearly edge‑on to Earth.
  • China’s Tianwen‑1 Mars orbiter released rare October images captured near the comet’s Mars passage, with CNSA reporting the nucleus and a several‑thousand‑kilometre‑wide coma resolved from about 30 million kilometres away.
  • NASA and ESA confirm 3I/ATLAS is on a hyperbolic, interstellar trajectory, with Hubble data placing the nucleus at no larger than 5.6 km and early spectra indicating carbon‑bearing volatiles consistent with cometary outgassing.
  • JPL has reported a small non‑gravitational acceleration likely linked to outgassing, while some commentators argue alternative explanations; agencies and many astronomers continue to describe the visitor as a natural comet.
  • After perihelion around October 29–30 and a period behind the Sun, the comet has reappeared to Earth observers, prompting coordinated tracking by space and ground assets including Hubble, JWST, ESA’s JUICE and Mars orbiters.