Last fall, a Sophia Sheikh’s colleague posted a message on her group’s Slack channel, where members of the Breakthrough Listen Search for Extraterrestrial Intelligence (SETI) collaboration talked about radio telescope signals they were analyzing for possible signs of communication from space. Much of what they have analyzed so far has clearly been due to radio interference on Earth, with countless works of human technology and scientists studying the frequency range at which they emit signals. But one seemed more promising.
The message was posted by a student studying radio telescope data which was originally taken to observe the stellar flames emitted by Proxima Centauri. He made a single unusual signal, and the sheikh did not know what to do with it. “It had a lot of features that we would associate with a signal coming from space,” he says. The detected signal near 982 MHz, dubbed “blc1” for “Breakthrough Listen Candidate 1”, aroused their curiosity from the outset, as it came from a telescope trained in our own nearby stellar system that could host a habitable world. And it looks narrow in the electromagnetic spectrum, suggesting that it was generated by technology. But Of which Technology?
In collaboration with other astronomers, Sheikh and his team began a series of experiments on signals – radio waves measured at different frequencies that stand above the more ubiquitous sound, such as the faint sound of a remote radio station, distinguished from static. They wanted to determine if the signal was something in the sky, and they compared it to the radio interference they encountered at other frequencies. And a pair of new studies published in the journal this week Nature Astronomy, They published their bad news: it was a false warning. The tantalizing signal did not come from space above all else, but originated from earthing technology like the others.
“This was the most promising signal we have ever received with the Breakthrough Listen Project,” said Sheikh, an astronomer at UC Berkeley and lead author of a research paper. But, he says, their year-long search for the study of mysterious signals and their origins was “the most exciting investigation of my career so far,” and has helped scientists develop their tools as they prepare to analyze future signals.
Breakthrough Listen, a research program that began in 2015, uses data from radio telescopes in Australia, West Virginia and California to listen to potential alien signals from nearby stars as part of an ongoing search for extraterrestrial civilization. Because it can be competitive to find time in a radio telescope, it sometimes involves “piggybacking” by stopping others from observing, so that they and other astronomers benefit from the same data.
Proxima Centauri seems to be a good candidate for the search for life outside our solar system. The star is “just” a little over four light-years from Earth or about 25 quadrillion miles away. It’s close from a cosmic perspective, and it’s within transition distance for a message of intelligent life. In 2016, astronomers confirmed the existence of a planet orbiting a star, raising hopes that it could be hospitable to alien life. If and when someone sends a space mission to another star, that will probably be their destination. In fact, the goal of Breakthrough Starshot is to create a system for firing a powerful laser beam so that a small spacecraft can be sent at high speed to the star’s neighbor Alpha Centauri, to be photographed and sent back home. (Both Breakthrough Listen and Starshot are funded by billionaire philanthropist Yuri Milner’s Breakthrough Initiatives.)