Astronomers from MIT registered a repeating signal from 500 million light years away. Such signals are called fast radio bursts, or FRBs, and they’re usually singular events. No one knows what their sources are, but they could be supernovae or bursts of energy from quasars. This repeating one, though, is pretty creepy because it’s regular: for four days, radio equipment captures signals all the time, and then they abruptly stop. But after 12 days, the same pattern begins: 4 days of constant radio bursts and 12 more days of silence.