CSIRO

Baffling radio burst traced to a galaxy 3.6 billion light-years away

Fast radio bursts (FRBs)—intense blasts of radio waves from distant galaxies—have perplexed astronomers since they were first detected a dozen years ago. The bursts are so brief, only about one-thousandth of a second, that it’s usually impossible to pinpoint their origins—or their cause, be it a supernova, a neutron star, or something even more exotic.

So far, almost all of the 85 detected FRBs are one-off events. But a couple have been seen to repeat, letting astronomers pinpoint where at least one of them comes from.

Now, researchers have localized a second FRB, this time a nonrepeater. The team used an array of 36 radio dishes called the Australian Square Kilometre Array (SKA) Pathfinder (above), a precursor instrument to the planned SKA in Western Australia. Because the FRB signal arrived at each dish of the widely spaced array at slightly different times, the team could analyze the lags, measured in fractions of one-billionth of a second, to pinpoint the source in the sky.

With the help of follow-up observations using some of the world’s largest optical telescopes, astronomers identified the burst, FRB 180924, as coming from a medium-size galaxy 3.6 billion light-years from Earth, they report today in Science. But this presents a puzzle for theorists: The previously localized FRB came from a particular type of dwarf galaxy that provided one of the few clues to what could cause FRBs. If the new find comes from a very different galaxy, does that suggest repeaters and one-offs have different causes? Only more detections and localizations will answer that question—perhaps using new purpose-built telescopes that are joining the hunt.