A radio signal detected by an Australian telescope in 2019, which seemed to be coming from the star closest to the Sun, was not from aliens, researchers report today in two papers in Nature Astronomy1,2.

“It is human-made radio interference from some technology, probably on the surface of the Earth,” says Sofia Sheikh, an astronomer at the University of California (UC), Berkeley, and a co-author of both papers.

But the disturbance, detected by Breakthrough Listen — an ambitious and privately funded US$100-million effort in the search for extraterrestrial intelligence (SETI) — looked intriguing enough at first that it sent astronomers on a nearly yearlong quest to understand its origins. It was the first time that data from Breakthrough Listen triggered a detailed search, and the experience puts scientists in a better position to study future candidate detections.