Astronomers Discover Mysterious Radio Signal From Proxima Centauri

Scientists searching for aliens are trying to understand the signal’s origins

Parkes Observatory
The Parkes Telescope in Australia David McClenaghan, CSIRO via Wikimedia Commons under CC BY-SA 3.0

Scientists detected a mysterious radio signal from a nearby galaxy, which begs the question—could it be aliens?

As part of the Search for Extraterrestrial Intelligence (SETI) program, astronomers working on the Breakthrough Listen project scan for radio signals that could come from some non-human intelligent life in the cosmos. This fall, researchers noticed evidence of a strange radio emission while looking through archival data from 2019. The odd radio emissions seemed to be coming from the direction of Proxima Centauri, the closest neighboring star to our sun at 4.2 light-years away, reports The Guardian's Ian Sample last week.

The scientists behind the discovery explain that there are several potential non-alien explanations for the strange signal. But they have yet to find a terrestrial culprit and have not yet ruled out an extraterrestrial intelligence origin story.

“It has some particular properties that caused it to pass many of our checks, and we cannot yet explain it,” Andrew Siemion, Breakthrough Listen’s principal investigator, tells Jonathan O’Callaghan and Lee Billings for Scientific American.

At the Parkes Observatory in Australia, the team uses a 210-foot-wide radio telescope to study Proxima Centauri. The star system is home to two planets, one of which may be rocky and temperate like Earth. There, they picked up a signal, dubbed BLC-1 after the Breakthrough Listen initiative.

BLC-1 is a narrow beam of around 982 megahertz. This signal is a far narrower frequency than what scientists typically can observe from human-made devices like satellites and spacecraft, according to Scientific American.

Additionally, there is an apparent shift in the beam’s frequency, which makes the finding especially compelling because it mimics the drift observed when planets in motion give off signals.

“It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before,” Sofia Sheik, a graduate student at Pennsylvania State University and the Breakthrough team member leading the signal analysis, tells Scientific American.

Though the wobbling frequency helps scientists rule out a terrestrial explanation for the signal, the beam could have come from a travelling satellite or other device. With the large volume of space technology orbiting the Earth and beyond, it can be extremely challenging to pinpoint which signals may be non-human-made, writes astronomer Seth Shostak for SETI.

“Our WiFi, our cell towers, our GPS, our satellite radio—all of this looks exactly like the signals that we’re searching for, which makes it very hard to tell if something is from space or from human-generated technology,” Sheikh tells Nadia Drake for National Geographic.

For nearly four decades, scientists at SETI have searched for signs of extraterrestrial life. In 2015, Silicon Valley investor Yuri Milner and Stephen Hawking began the Breakthrough Initiatives. Using telescopes around the world, astronomers with Breakthrough survey millions of stars closest to Earth, searching for planets in the habitable zone of stars and for transmissions from other intelligent life.

Over the years, astronomers have identified several candidate signals, writes National Geographic. Some led to the discovery of natural phenomena like pulsars—quickly rotating neutron stars or white dwarfs that emit electromagnetic radiation beams. Another mysterious low-energy burst of radio waves stumped scientists until they discovered it was no more than a microwave oven in the radio telescope’s break room.

“All of our SETI experiments are conducted in an absolute sea of interference. There are tons of signals,” Siemion tells National Geographic. “It comes down to being able to tell the difference between a very distant technosignature and our own technology.”

The team is preparing two papers describing the signal to be published in 2021, according to Scientific American. The detection was leaked to The Guardian before the papers were complete. The researchers have yet to reobserve the signal, but they will continue to focus attention on Proxima Centauri.

“There’s a lot of talk about sensationalism in SETI,” Siemion tells National Geographic. “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!”