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Sun-Facing Tail in Interstellar Comet 3I/ATLAS Reveals Wobbling Jets, Suggesting 15.5-Hour Rotation

A 37-night campaign found precessing jets in a sunward anti-tail, implying a roughly 15.5-hour spin.

Overview

  • Researchers observed jet features precessing about every 7 hours 45 minutes inside a rare sunward anti-tail, from which they infer a nucleus rotation period near 15 hours 30 minutes.
  • NASA’s Parker Solar Probe captured WISPR images of 3I/ATLAS from October 18 to November 5 when it was too close to the Sun to be seen from Earth, with final calibration and processing underway.
  • The Allen Telescope Array’s July 2 search reported no localized radio signals from the object after extensive RFI filtering, setting upper limits of roughly 10–110 watts across 1–9 GHz.
  • Millimeter observations detected methanol and hydrogen cyanide in the coma, and scientists assess any cyanide-bearing dust or gas reaching Earth as negligible given the distance and atmospheric shielding.
  • 3I/ATLAS is forecast to pass about 33.3 million miles from Jupiter on March 16, 2026, presenting a key opportunity to refine trajectory and activity models with additional observations.