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Interstellar Visitor 3I/ATLAS Shows Reported SunwardAnti-Tail’ Ahead of Perihelion

Keck-based claims of a sunward anti-tail with unusual gas emissions remain unreviewed as most scientists expect ordinary comet behavior.

Overview

  • Keck II observations in August identified a tendril pointing toward the Sun, and a recent preprint reports cyanide and nickel outgassing both sunward and anti-sunward as support for an anti-tail, though the paper has not been peer reviewed.
  • 3I/ATLAS reaches solar conjunction on October 21, placing it behind the Sun from Earth just as it nears perihelion on October 29.
  • Mars-orbiting spacecraft have already recorded activity, and brief views may be possible next month during a Jupiter pass by NASA’s Juno and ESA’s Juice.
  • Experts note natural mechanisms can create a sunward feature, citing projection effects and slow ejection of large dust grains from a rotating nucleus.
  • Avi Loeb has highlighted the anti-tail and gives the object a 4 out of 10 on his personal scale, while NASA’s small-bodies lead says the evidence points to a normal comet.