3I/ATLAS: FAST Reports a Periodic-Signal Radio Null — The Second Independent SETI-Style Test Comes Back Empty
A measured account of the day's principal case under Council review, with citation, location, and verdict status.
A preprint posted to arXiv on 2026-07-15 (arXiv:2607.01666) reports the first search for periodic radio emission from interstellar comet 3I/ATLAS using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in Guizhou, China. Across the observing campaign, no statistically significant periodic signal was detected in any of the searched frequency bands, timing folds, or duty-cycle windows. The Council files the finding as Confirmed at the null-result level: FAST is the world's most sensitive single-dish radio telescope, and its non-detection is the second independent SETI-style test on 3I/ATLAS to come back empty, following the Allen Telescope Array survey summarised in Case #00494. The result further softens the technosignature hypothesis on the Loeb branch while updating no verdict on the natural-origin branch — the object continues to look like a natural interstellar comet on every evidentiary channel the Council has to hand.