A Strange Radio Signal Was Just From Earth, Not Aliens

When an intriguing signal like blc1 appears, people love to ask questions like: “Do we message back?” says Danny Price, an astronomer at the International Centre for Radio Astronomy Research in Perth, Australia, and an author of the other new paper. But it takes a lot of work following the initial detection before astronomers can make the call whether the signal’s the real deal or just interference from Earth. “I don’t think when we find something it’s necessarily going to be a really clear signal, like in Contact. It’s going to be a low signal-to-noise, difficult-to-interpret signal that needs a lot of verification,” he says.

Contact, Carl Sagan’s novel, was made into a movie in 1997. Sagan based the protagonist, played in the film by Jodie Foster, on Jill Tarter, a leader in the SETI field and founder of the SETI Institute in Mountain View, California. While Tarter and other early SETI researchers sometimes struggled for funding and support, that’s not really the case anymore, says Jason Wright, an astronomer at Penn State University. He argues that Breakthrough Listen, based near the SETI Institute at UC Berkeley’s SETI Research Center, played a role in that improved status.

“I think Breakthrough Listen has breathed new life into the field. It has given the field much more visibility and scientific respectability. I think it’s entirely appropriate that they’re finally getting the telescope time worthy of the question they’re trying to answer,” Wright says. (He previously served as Sheikh’s thesis adviser but was not involved in this project.)

When SETI research began, astronomers didn’t have to contend with as much radio interference. But it has gotten worse, thanks to the proliferation of cell towers, satellites and satellite constellations, and today there are few places remote enough to avoid it. “The only place in the whole solar system that is almost free of radio interference is the far side of the moon. I say ‘almost’ because there are lunar orbiters, so it’s begun,” Wright says. (NASA has given early funding to two projects that are coming up with designs for a lunar radio telescope.)

New and updated Earthbound telescope arrays will soon help expand the search for radio signals from aliens, by enabling sensitive observations of many stars at once, in the hopes of spotting a real alien signal from any one of them. “The SETI Institute was a pioneer with array technology, with the development of the Allen Telescope Array,” says Andrew Siemion, an astronomer at the SETI Institute and a co-author of the new studies. The array is currently being refurbished and upgraded with new technologies, he says. It consists of 42 antennas, and it’s based at Hat Creek Observatory, about 300 miles north of San Francisco. The Dixie Fire in September burned within a few miles of the array, but the telescopes were spared.

Sheikh, Price, and their colleagues plan to continue monitoring Proxima Centauri and other targets with another radio telescope array, in the Northern Cape of South Africa, called MeerKAT. It currently has 64 satellite dishes, each 13.5 meters in diameter.

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