Scientists engaged in the search for advanced alien civilizations have identified a mysterious radio signal within data gathered by China's Five-hundred-meter Aperture Spherical radio Telescope (FAST), the largest single-dish radio telescope globally.
The signal, designated NBS 260108, was detected by a Chinese-led team while they were testing new analysis software on existing FAST observations. It appeared as a steady radio tone concentrated around a single frequency and was specifically observed in telescope beams pointed towards the K2-155 star system, located approximately 238 light-years from Earth. This system hosts three "super-Earths," one of which orbits near its star's habitable zone.
Researchers consider such narrowly focused signals to be significant targets in the search for extraterrestrial technology because natural cosmic phenomena rarely produce them, whereas artificial transmitters often do. The signal stood out further as it was detected only in the beam directed at K2-155, with no corresponding signal appearing in the telescope's 18 other simultaneous observation beams.
Additionally, the signal's frequency shifted steadily over time, a pattern that scientists examine for evidence of transmissions from distant technology. The team noted that the K2-155 system was a compelling target for SETI (Search for Extraterrestrial Intelligence) efforts due to its habitable-zone super-Earth, K2-155d, which is about 1.6 times Earth's radius and orbits its star every 40.7 days.
While the software successfully identified the signal as a candidate worth investigating, the researchers emphasized that candidate generation and interpretation remain separate processes. Future work may involve comparing original recordings from all 19 telescope beams to better pinpoint the signal's location and motion, which could help distinguish between extraterrestrial transmissions and interference from human technology or equipment.
The FAST telescope's vast collecting surface, measuring approximately 1,640 feet across, grants it exceptional sensitivity to faint radio waves from space. The new study, published in The Astronomical Journal, analyzed FAST observations of 33 planetary systems collected in 2021.
The signal's drift towards a lower radio frequency and its distinct response in the telescope's polarization channels—strongly present in one channel (YY) but absent in another (XX)—further characterized the detection. The observation occurred on September 10, 2021, as part of a sequence that also included data from other star systems.