In December last year, the media reported an intriguing signal we at the Breakthrough Listen project found in our radio telescope data.

Today we are ready to report that BLC1 is, sadly, not a signal from intelligent life beyond Earth.

Rather, it is radio interference that closely mimics the type of signal we've been looking for.

The story of BLC1 starts in April 2019, when Andrew Zic, who at the time was a PhD student at the University of Sydney, began observing the nearby star Proxima Centauri with multiple telescopes to search for flare activity.

While bad space weather doesn't rule out life existing in the Proxima Centauri system, it does mean the planet's surface is likely to be inhospitable.

BLC1 is the yellow drifting line, and is only present when the telescope is pointed at Proxima Centauri.

Toward the end of his project, BLC1 popped out.

we only saw BLC1 when we were looking toward Proxima Centauri, and didn't see it in when we looked elsewhere (in "off-source" observations).

the BLC1 signal persisted for several hours, making it unlike other interference from artificial satellites or aircraft that we have observed before.

Nevertheless, Sofia's analysis led us to conclude BLC1 is most likely radio interference from right here on Earth.