In November 2012, a powerful blast of radio waves hit the Earth. This event—called a fast radio burst—intrigued scientists with its extreme energy, faraway origin, and seeming lack of clues about whatever mysterious astrophysical engine had blasted the waves into space.
But unlike the few fast radio bursts that had been observed before, this one was destined to be more than a one-hit wonder.
In early 2015, another blast of radio waves was fired by the same unknown engine. And another. And then another, and another, until finally, over a period of three hours, a total of ten additional bursts emerged from the same location on the sky.
It’s the first time astronomers have caught a fast radio burst in the act of repeating, and—as reported this week in Nature—the observations provide crucial clues about the origin of these bursts, which have stumped astronomers for nearly a decade.
“I just plain love this discovery,” says astronomer Emily Petroff of the Netherlands Institute for Radio Astronomy. “The observations and data are very solid. A super fascinating result and definitely a really big deal.”
Astronomers used the world's largest single-dish radio telescope, the Arecibo Observatory in Puerto Rico, to search for enigmatic blasts of radio waves. [Photograph By Universal Images, Getty]
Until now, fast radio bursts were generally thought to be the result of cataclysmic, one-time astrophysical events such as supernovas, stars collapsing into black holes, or colliding stars. That’s because no one had ever seen a burst go off more than once. But if the same source continues firing radio waves into space, that rules out a bunch of ideas. It’s not like a supernova can put the band back together and go on a revival tour.
“If it happened four years ago and it’s happening again now, it’s not some star that collapsed or black holes that merged,” says study co-author Scott Ransom of the National Radio Astronomy Observatory. “This is probably a very young, very fast spinning magnetar, in some local-ish galaxy, that occasionally goes into semi-outbursty form.”
Blasts from the Past
First detected in 2007, fast radio bursts have been a stubborn, messy puzzle to solve. Including these 10 new ones, roughly two dozen of the bursts have been observed, and many appear to be coming from billions of light-years away. Yet they last for just thousandths of a second. For years, scientists have argued over whether the bursts were really coming from outside the Milky Way galaxy—and whether the bursts were even real or were artifacts produced by telescopes on Earth.
As more observations trickled in, astronomers gradually began to agree that yes, the bursts are real, and yes, they do appear to be coming from far away. But their origins eluded capture.
Recently, an important piece of puzzle snapped into place when a team of scientists studying the large-scale structure of the universe serendipitously snared a burst that contained a new, essential piece of information: In addition to coming from very far away, the burst appeared to have traveled through a highly magnetized region of space, suggesting that perhaps a flaring, extremely magnetic neutron star—a magnetar—could be spinning away at its origin.
It’s a story that matches these new observations, and it could be a window into the world of at least one burst engine.