3I/ATLAS: Interstellar Giant's Enigma – No Extraterrestrial Signals, Yet Oddities Abound
The planet's most advanced radio observatory detected no artificial transmissions from 3I/ATLAS, the biggest interstellar body ever spotted. Breakthrough Listen's latest findings spotlight the enigmatic intruder's bizarre traits, keeping astronomers enthralled.
On December 18—one day before perihelion—the 100-meter Green Bank Telescope in West Virginia swept frequencies from 1 to 12 GHz. Led by UC Berkeley's Ben Jacobson-Bell, the team flagged 471,198 candidate signals initially. After weeding out terrestrial interference, nine lingered—all human artifacts. The SETI Institute declared, "No engineered radio emissions tied to 3I/ATLAS were found." It could pick up signals as faint as a cellphone's 100 milliwatts.
Record Dimensions and Peculiar Composition
As the third verified interstellar object after 'Oumuamua (2017) and 2I/Borisov (2019), 3I/ATLAS reigns as the largest. Spotted July 1, 2025, by Chile's ATLAS array, its core spans 440 meters to 5.6 kilometers, or up to 7 miles per some models.
James Webb Space Telescope data showed a coma of 95% carbon dioxide and just 5% water. The Very Large Telescope spotted atomic nickel vapor sans matching iron—a trait evoking man-made metals over cosmic rocks. Hubble's late-December snaps revealed three jets blasting from the nucleus at precise 120-degree intervals, crafting symmetry, plus a colossal "anti-tail" aimed sunward. Harvard's Avi Loeb documented over 15 quirks, urging deeper probes.
Contention on Natural Provenance
Mainstream experts deem 3I/ATLAS a quirky yet innate comet. NASA's Amit Kshatriya stated in November, "It's a comet—appearance and actions confirm it."
The Breakthrough Listen squad noted "mostly standard cometary hallmarks, like a coma and compact nucleus," but cautioned "With merely three known, and interstellar craft plausible as technosignatures, rigorous scrutiny is essential."
Now faintly visible (+15.6 magnitude) in Leo via major scopes, this potentially 8-13 billion-year-old relic will graze Jupiter on March 16, 2026, before fading into the cosmic void eternally.
