Astronomers have detected a rare radio signal that originated about 3 billion years ago in a galaxy far, far away. And as one expert puts it, the source is "kind of perplexing." Fast radio bursts, millisecond-long pulses of radio emission from beyond our galaxy, were first discovered a decade ago. Since then, scientists have detected only 30 of them, generally believed to be caused by colliding black holes or other cataclysmic events, per Popular Science. FRB 121102, however, is a curious anomaly. Traced to a dwarf galaxy some 3 billion light years away, FRB 121102 was detected in 2012 and again in 2015, making it the only FRB known to repeat. And now scientists say it's emitting bursts again. Using a radio telescope in West Virginia on Saturday, UC Berkeley researchers detected 15 new pulses from FRB 121102 at a much higher frequency than ever before.
"As the source is going into another active state [that] means that the origin models associated with some sort of cataclysmic events are less likely to be the case of FRB 121102," researcher Vishal Gajjar tells CNET. Could the bursts have come from aliens and their spacecraft? That's a "less popular theory," as CBC News puts it, with Popular Science going into greater detail on "possible explanations for the repeating burst ... most of them are definitely not aliens." Here's one: that the bursts came from an energetic neutron star. A statement on the find gives some perspective: "Regardless of FRB 121102’s ultimate source, when the recently detected pulses left their host galaxy ... life on Earth consisted only of single-celled organisms." (Read about the discovery of repeating FRBs here.)