Scientists have detected a mysterious radio signal originating from a star system approximately 238 light-years from Earth. The signal, named NBS 260108, was identified by a Chinese-led team while testing new software on data collected by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), the world's largest single-dish radio telescope.
The signal was observed in data from the K2-155 star system, which hosts three 'super-Earths,' including one planet situated near its star's habitable zone. It appeared as a steady radio tone concentrated around a single frequency, a characteristic that is of significant interest in the search for extraterrestrial technology. Natural cosmic processes rarely produce such narrowly focused signals, while artificial transmitters often do.
The signal stood out because it was detected only in the telescope's beam aimed at K2-155, with no corresponding detection in the other 18 beams simultaneously observed. Additionally, its frequency shifted steadily over time, a pattern scientists look for when searching for transmissions from distant technology. The researchers described the investigation as addressing "one of humanity’s oldest scientific questions - whether intelligent life exists beyond Earth."
FAST's immense collecting surface, measuring roughly 1,640 feet across, makes it particularly sensitive to faint radio signals. The telescope is built into a natural basin in southwestern China.
The new study, published in The Astronomical Journal, analyzed FAST observations of 33 planetary systems collected in 2021. The K2-155 system was a target of interest due to its outer planet, K2-155d, which is located near the star's habitable zone, a region where conditions might allow liquid water to exist on a planet's surface. This planet is approximately 1.6 times Earth's radius and orbits its star every 40.7 days.
The research team focused on identifying radio transmissions that could indicate technology developed by an advanced civilization, rather than searching for biological clues. A distant transmitter's movement relative to Earth can cause its signal's frequency to shift over time, creating a drifting track in telescope data. The observed signal gradually shifted to a lower radio frequency.
While the signal's characteristics make it a compelling candidate for further investigation, the researchers emphasize that spotting an unusual signal and establishing its source are distinct challenges. "Candidate generation and candidate interpretation should remain separate," they wrote. Future improvements in distinguishing between extraterrestrial transmissions and terrestrial interference could involve comparing original recordings from all 19 telescope beams to better determine a signal's position and motion.