Astronomers Finally Tracked a Strange Radio Wave Burst to Its Source

With new insights into radio waves, scientists may be able to measure the mass of the universe

CSIRO's Compact Array telescope picked the Fast Radio Burst's afterglow. Alex Cherney/CSIRO

Update April 5, 2016: New research on the fast radio burst detected in February suggests that it may not have been a fast radio burst at all. According to a new study of the data published this week in Astrophysical Journal Letters, astronomers from Harvard University following up on the research discovered that the source is likely a supermassive black hole at the center of the distant galaxy, not a fast radio burst. The astronomers say that the variations in the radio signal’s strength may be due to it passing through interstellar gases, causing it to twinkle like stars seen through the Earth’s atmosphere.

For nearly a decade, astronomers have been puzzled by a mysterious phenomenon: brief, powerful bursts of radio waves coming from deep space. Now, thanks to a global network of telescopes working to triangulate the source of these pulses, astronomers not only know where the latest radio burst came from, but can use that information to help measure the mass of the universe.

These strange pulses, known as fast radio bursts or FRBs, last only a fraction of a second but are strong. To produce this millisecond burst requires about as much energy as our own sun emits in days, or even weeks, Jonathan Webb writes for the BBC.

FRBs are also uncommon: this most recent radio burst was only the 17th one recorded since they were first discovered in 2007. Because they last for such a short period of time, these mysterious radio waves have been tricky for astronomers to identify and study before they slip away.

"A decade ago, we weren't really looking for them—and also our ability to handle the data and to search it in a reasonable time was significantly poorer," astronomer Evan Keane tells Webb. "Whereas with this one, I was awoken by my phone going crazy a few seconds after it happened, saying: Evan, wake up! There was an FRB!"

While astronomers have studied these radio bursts by combing through archival data, Keane wanted to catch one in the act. So he set up a network of telescopes from around the world to help pinpoint the FRB shortly after detection, Joe Palca reports for NPR. A supercomputer monitored the incoming telescopes to notify scientists as soon as the FRB began. Then when the big moment finally arrived, Keane and his colleagues sent out the call to telescopes from Australia to Hawaii to help them track down the source of the radio burst.

"There's only one thing there, and it's a galaxy, an elliptical galaxy,” Keane tells Palca.

Using data from several radio telescopes, Keane and his team traced the FRB to a galaxy halfway across the universe, about 6 billion light years away. It doesn’t explain exactly what caused this radio burst, but there are a few theories—none of which include aliens.

Elliptical galaxies are usually older, meaning no new stars have formed there for a very long time. So the radio burst was not likely caused by a supernova, which is the death of a short-lived massive star and are not common in elliptical galaxies, Phil Plait writes for Slate’s Bad Astronomy blog.

It is more likely that the burst was created by two massive neutron stars merging together into a black hole. Neutron stars are the remnants left behind when a star explodes. They are incredibly dense, and if two are close enough, they can coalesce into a black hole—a violent event that can throw short bursts of energy out into the cosmos, much like the FRB Keane observed, Plait writes.

While astronomers may not know exactly what caused the radio burst, watching it in real time has had an interesting side effect. Keane and his colleagues now know how far away the FRB traveled and how the different radio frequencies in the burst are staggered. So they can use that delay to figure out how many particles and how much cosmic dust the waves travled through to get to Earth—in effect, measuring the density of that part of the universe.

According to current models of the universe, what scientists observe as matter only makes up about 5 percent of everything out there. Until now, astronomers haven’t been able to directly look at the other 95 percent, but this new information clues them into how they can find that so-called “missing matter,” Webb writes.

"We measured this delay, and if you work out how much matter must be there to cause it—it's right,” Keane tells Webb. “The missing matter is missing no more."

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