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Interstellar Comet 3I/ATLAS Reappears Brighter and Bluer After Solar Flyby

A global campaign is pivoting to Dec. 19, when the visitor passes 1.8 AU from Earth for the most detailed study.

Overview

  • Astronomer Qicheng Zhang captured the first post‑perihelion images around Oct. 31–Nov. 2, showing the object unexpectedly brighter with a distinctly blue hue.
  • NASA’s Neil Gehrels Swift Observatory detected hydroxyl in ultraviolet light, confirming active water outgassing at unusually large solar distances.
  • NASA and ESA report the body is on a hyperbolic trajectory exceeding ~210,000 km/h, with a closest‑Earth approach on Dec. 19 at about 1.8 AU (~270 million km) and no danger to the planet.
  • Hubble observations set an upper limit of roughly 5.6 km for the nucleus diameter, while larger size estimates circulating in media remain unconfirmed.
  • Multi‑instrument observations continue through early 2026, as contested claims of anomalous acceleration, nickel‑rich ejecta and artificial origin face scrutiny against accumulating data.