Billions of years ago, an unknown object sent a seriously bright burst of radio waves into space. They traveled across the universe, past galaxies and clouds of gas and who knows what else. And in 2012, the burst arrived at the Arecibo radio telescope when astronomers happened to be watching. They kept searching that same spot in the sky. In 2015, they found 16 additional flashes. Then, in August and September 2016, nine more appeared.