Radio waves are invisible to our eyes. But if you could see them, the sky would dance with random tiny flashes. Thousands of what are called “fast radio bursts” are estimated to occur every day. And though each pinprick flash lasts only a thousandth of a second, they represent a faraway source briefly shining a billion or more times brighter than our sun.

Fast radio bursts have been known for nearly a decade, but scientists have struggled to determine exactly where they come from. And they’d like to know. Because finding their origins would help astronomers use the bursts as probes to map the history and structure of the universe in unprecedented detail.

Now researchers have found the source of one particular burst. They used radio telescopes in Australia and the giant Subaru optical telescope in Hawaii to trace a burst observed last April. And they determined it came from an old elliptical galaxy full of exhausted, dying suns some six billion light-years away. The findings are in the journal Nature. [Link to come]

Identifying the source galaxy provides crucial clues. For one thing, such a galaxy is short on some of the objects expected to cause bursts, such as supernovae or rapidly spinning and flaring pulsars, suggesting this burst came from something else. And, although the burst in question lasted only milliseconds, astronomers were able to witness its faint, fading radio afterglow for about six days. That’s the sort of afterglow expected from a colliding pair of ancient neutron stars, which would be a relatively common occurrence among an elliptical galaxy’s geriatric suns.

Even though this particular burst has probably been explained, many mysteries remain—not all bursts seem to come from the same cosmic source. Fortunately, most possible burst sources could be distinguished by the gravitational waves they emit, like those recently seen by the Laser Interferometer Gravitational-Wave Observatory, or LIGO. That means researchers may soon be searching the skies for both radio and gravitational waves for these bursts, to help draw an ever more detailed map of the cosmos.

—Lee Billings

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]