Recent research from astronomers at the University of California, Berkeley, confirms that a puzzling radio signal once thought to hint at extraterrestrial life near Proxima Centauri originated on Earth.
Several months ago, astronomers using Australia's Parkes (Murriyang) radio telescope detected an unusual radio signal from the direction of Proxima Centauri, our solar system's nearest neighbor at just 4.2 light-years away. In a 26-hour observation, the telescope captured over four million signals, but one standout radio burst lasted about five hours and featured a distinctive narrowband wavelength.
This narrowband signal occupied only a narrow range of radio frequencies (982 MHz), a trait typically associated with human satellites that compress signals into single frequency bands. The team ruled out satellites as the source.
Proxima Centauri is known to host Proxima b, a potentially habitable Earth-sized rocky exoplanet. The signal, named Breakthrough Listen Candidate 1 (BLC-1), even appeared to "evolve" slightly over its five-hour duration, hinting at a planetary origin from a moving source.
This sparked excitement among SETI researchers. However, detected only once in spring 2019, follow-up observations failed, leading skeptics to suspect terrestrial radio interference. They were correct.
"It was man-made radio interference from technology, probably on Earth's surface," explains Sofia Sheikh, a UC Berkeley researcher and co-author of two studies published in Nature Astronomy.
With the signal absent in later scans, the team re-examined original data. Their analysis revealed similar signals ignored by initial software, but at different frequencies.
These signals, including BLC-1, traced back to a single Earth-based radio source, likely a few hundred kilometers from the telescope. Its appearance during the Proxima observation was coincidental.
Never repeating, the signal likely stemmed from faulty electronics. Its frequency matched "common clock oscillator frequencies in digital electronics," per the researchers—possibly a nearby phone or computer. Further investigations aim to pinpoint the exact source.
