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MeerKAT’s First Radio Detection of 3I/ATLAS Confirms Water Outgassing

The OH absorption seen on October 24 ties the interstellar visitor’s coma to classic cometary physics, undercutting claims of an artificial source.

Overview

  • South Africa’s MeerKAT telescope recorded hydroxyl absorption from 3I/ATLAS on October 24, the object’s first radio detection, revealing water molecules produced by sunlight breaking apart vapor in its coma.
  • The team reported non-detections on September 20 and 28 before the clear signal near perihelion on October 29–30, showing the rise in activity expected for an active comet.
  • Post-perihelion imaging shows powerful jets, a pronounced anti-tail, and a growing ion tail, yet observers report no evidence that the nucleus fragmented.
  • Astronomers say the measurements fit a natural interstellar comet despite unusual chemistry and morphology, rejecting assertions that the signal or behavior indicates alien technology.
  • Further monitoring is underway, with the comet’s closest approach to Earth expected around December 19 at roughly 1.8 AU and a potential observing opportunity near Jupiter for NASA’s Juno in March 2026.