The mysterious signals were first detected in 2020 by the Breakthrough Listen project, which hunts for evidence of alien “technosignatures” — radio waves and other evidence of extraterrestrial technology.
The initiative uses some of the largest radio telescopes in the world to capture data across broad swaths of the radio spectrum in the direction of a wide range of celestial targets.
One of Breakthrough Listen’s targets is Proxima Centauri. The star, located slightly more than 4 light-years from Earth, is a red dwarf orbited by two known exoplanets.
Found this autumn in archival data gathered last year, the signal appears to emanate from the direction of our neighboring star and cannot yet be dismissed as Earth-based interference, raising the very faint prospect that it is a transmission from some form of advanced extraterrestrial intelligence (ETI)—a so-called “technosignature.”
Now, speaking to Scientific American, the scientists behind the discovery caution there is still much work to be done, but admit the interest is justified. “It has some particular properties that caused it to pass many of our checks, and we cannot yet explain it,” says Andrew Siemion from the University of California, Berkeley.
Most curiously, it occupies a very narrow band of the radio spectrum: 982 megahertz, specifically, which is a region typically bereft of transmissions from human-made satellites and spacecraft. “We don’t know of any natural way to compress electromagnetic energy into a single bin in frequency” such as this one, Siemion says.
Perhaps, he says, some as-yet-unknown exotic quirk of plasma physics could be a natural explanation for the tantalizingly concentrated radio waves. But “for the moment, the only source that we know of is technological.”
The detection was made by a $100 million project called Breakthrough Listen, led by Siemion and funded by tech billionaire Yuri Milner under the umbrella of Milner’s Breakthrough Initiatives.
The goal of this multiyear endeavor—which began in 2015 with a star-studded announcement attended by Stephen Hawking and other space-science luminaries—is to buy observing time on radio telescopes around the world to search the skies for evidence of technological civilizations.
“It’s pretty expected that every now and then you’ll see something weird, but this is interesting because it’s something that’s weird that we’re having to think about the next steps,” says Sofia Sheikh, a graduate student at Pennsylvania State University and the Breakthrough team member leading the signal analysis.
Though Sheikh and others strongly suspect that the signal is really human in origin, BLC-1 is the most tantalizing detection Breakthrough has made so far in its search for extraterrestrial intelligence, or SETI.
The team is preparing two papers describing the signal and a follow-up analysis, which isn’t yet complete. (The detection was leaked to The Guardian before the research was ready for publication.)
That pursuit, of course, is more commonly known as the Search for Extraterrestrial Intelligence (SETI). To date, no such evidence has conclusively been found despite more than a half century of modest-but-steady SETI activity, with any potential signals almost always ruled out as originating from satellites orbiting Earth or other human-caused interference.
While researchers continue to analyze the signal—and experts caution that there is almost certainly an ordinary, terrestrial explanation—even a remote hint of life beyond Earth has people excited.
“There’s a lot of talk about sensationalism in SETI,” says Andrew Siemion, Breakthrough Listen’s principal investigator. “The reason we’re so excited about SETI, and why we dedicate our careers to it, is the same reason why the public gets so excited about it. It’s aliens! It’s awesome!”