In a thousandth of a second on April 28, a powerful burst of radio waves washed over Earth, lighting up radio telescopes in North America. Now, astronomers have tracked down the source of this strange signal—and the results could reveal the long-sought cause of some of the most mysterious cosmic signals ever recorded.

In three studies published today in the journal Nature, an international group of scientists identified the blast as a fast radio burst, an extremely intense flash of radio waves that lasts no more than a few milliseconds. Telescopes have picked up such bursts before, but always from outside our galaxy. Researchers have wondered for years what could cause these ephemeral but powerful blasts, with speculation ranging from exploding