Scientists have detected repeating radio signal bursts coming from a galaxy located 1.5 billion light years away, The Independent reports. Among 13 radio signal bursts detected within the past three weeks, one signal reportedly repeated six times from the same location, marking only the second time ever scientists have spotted a repeating radio burst, according to a new paper published in Nature. The signals, known as FRBs, reportedly only last for a millisecond and are eliminated with the same amount of energy the sun produces in a year. The source behind them remains a mystery, with everything from extraterrestrial life to exploding stars cited as the possible cause. “Until now, there was only one known repeating FRB. Knowing that there is another suggests that there could be more out there. And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles—where they’re from and what causes them,” Ingrid Stairs, a CHIME observatory scientist at the University of British Columbia was quoted as saying. Seven of the signals were reportedly recorded at the lowest frequency discovered (400 MHz), suggesting there may be more radio signals too low in frequency to be detected with current technology.