Scientists detect mysterious radio signal in search of alien life

Scientists searching for alien life have picked up a mysterious radio signal.A Chinese-led team detected it while testing new software on existing data from China’s FAST telescope, the world’s largest single-dish radio telescope.The signal surfaced in observations of K2-155, a star system about 238 light-years from Earth that hosts three ‘super-Earths,’ including one near its star’s habitable zone.Named NBS 260108, it appeared as a steady radio tone concentrated around a single frequency.Such narrowly focused signals are a key target in the search for alien technology, because natural cosmic processes rarely produce them while artificial transmitters often do.The signal stood out because it appeared only in the telescope beam aimed at K2-155, with no corresponding detection in the other 18 beams.Its frequency also shifted steadily over time, a pattern scientists examine when searching for transmissions from distant technology.The researchers described the search as addressing ‘one of humanity’s oldest scientific questions - whether intelligent life exists beyond Earth.’ The signal (pictured) surfaced in observations of K2-155, a star system about 238 light-years from Earth that hosts three ‘super-Earths,’ including one near its star’s habitable zoneBut spotting an unusual signal and establishing its source are separate challenges.‘Candidate generation and candidate interpretation should remain separate,’ they wrote.In other words, software can identify something worth investigating without establishing what produced it.The team says future improvements could involve comparing the original recordings from all 19 telescope beams to help determine a signal’s position and motion.Those additional checks could give researchers stronger evidence for distinguishing transmissions arriving from space from interference generated by human technology or equipment.FAST’s enormous collecting surface makes it especially sensitive to faint radio signals. Built into a natural basin in southwestern China, its dish measures roughly 1,640 feet across and covers an area equivalent to about 30 soccer fields. That vast surface gathers weak radio waves from space, allowing researchers to detect signals that smaller telescopes might miss. A Chinese-led team detected it while testing new software on existing data from China’s FAST telescope, the world’s largest single-dish radio telescopeThe new study, published in The Astronomical Journal, tested the software on FAST observations of 33 planetary systems collected in 2021.Super-Earths are planets larger than Earth but smaller than ice giants such as Neptune and Uranus.K2-155 was an intriguing target because its outer planet, K2-155d, lies near the star’s habitable zone, where conditions could allow liquid water to exist on a planet’s surface.The planet is approximately 1.6 times Earth’s radius and completes an orbit around its star roughly every 40.7 days.‘This system’s habitable-zone super-Earth made it an intriguing SETI [the Search for Extraterrestrial Intelligence] target,’ the team wrote, referring to the search for extraterrestrial intelligence.One light-year is approximately 5.88 trillion miles - the distance light travels in one year.Rather than searching for biological clues, the researchers focused on radio transmissions that could indicate technology developed by an advanced civilization.A distant transmitter’s motion relative to Earth can cause its signal’s frequency to shift over time, creating a drifting track in telescope data.The signal gradually shifted to a lower radio frequency, like a station slowly moving down the dial. Its appearance in only one of FAST’s 19 receiver beams initially made it worth examining. That beam was aimed at K2-155, while the other 18 showed no corresponding detection.On the researchers’ charts, it formed a thin, slightly slanted streak against the surrounding background. That streak traced how the signal’s frequency changed over time.FAST recorded it through the receiver beam pointed at K2-155. The telescope’s other 18 beams, which monitored neighboring patches of sky simultaneously, showed no corresponding detection.The signal also had a distinctive response in the telescope’s two polarization channels, which measure different orientations of radio waves.It appeared strongly in the channel called YY but was absent from the other, XX. In YY, its signal-to-noise ratio was approximately 23, a measurement of how clearly it stood above the background noise. When the two channels were combined, that measurement was approximately 15.The observation was part of a September 10, 2021, sequence that also included the stars K2-18, GJ-9066 and Ross 128.Researchers found other narrow radio features at nearby frequencies during those observations, although their characteristics differed. The K2-18 feature was very weak, the GJ-9066 feature barely shifted in frequency, and the Ross 128 feature appeared at a slightly different frequency.