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Interstellar Comet 3I/ATLAS Nears Dec. 19 Flyby as New Data Point to Two Tails and Unusual Chemistry

A global observing campaign intensifies with JUICE’s full dataset not expected until late February 2026.

Overview

  • Closest approach occurs on December 19 at roughly 1.8 AU (about 270 million km) from Earth, and agencies reiterate there is no impact threat.
  • Hubble and ESA releases show a bright coma with indications of both a plasma tail and a fainter dust tail, confirming sustained activity after perihelion.
  • Atacama Compact Array measurements report methanol at about 8% of vapor output (~40 kg/s) and hydrogen cyanide at 0.25–0.5 kg/s, pointing to atypical abundance ratios.
  • Observations document a 16.16-hour brightness pulse consistent with rhythmic jets; speculative claims remain unconfirmed, and NASA and ESA describe a natural comet.
  • ESA’s JUICE observed the object with five instruments and shared a preliminary NavCam view, with full instrument data expected to reach Earth in late February 2026.