Fast-radio bursts have puzzled astronomers for more than a decade. Now a new type of these powerful-yet-brief bursts of radio waves that traverse the vast expanse of intergalactic space has been discovered. Their source is still unknown.
A team of scientists has discovered another piece of the puzzle that might shed more light on a mysterious astronomical phenomenon.
Fast radio bursts, or FRBs, are powerful flashes of radio waves, lasting only a few milliseconds, that traverse the vast distance of space. The first one was discovered in 2007 after astronomers went through data collected in 2001.
At first, most were one-offs — a flash and then they were gone. But in 2015 Paul Scholz, then an astronomer at McGill University, found one that repeated, though not with any regularity.
Now, a new discovery by a team of astronomers using the Canadian Hydrogen Intensity Mapping Experiment telescope (CHIME) at the Dominion Radio Astrophysical Observatory in Okanagan Falls, B.C., has made the first discovery of an FRB that repeats on a regular basis. It’s relatively close to Earth in astronomical terms: just 500 million light years away.
The discovery might help astronomers reveal what is exactly causing these immensely powerful bursts to help scientists better understand how the universe works.
This new FRB, designated FRB180916.J0158+65, is the first to produce a periodic pattern. It begins to produce bursts within a four-day window followed by 12 days of silence, for a total period of 16 days.
“We’ve been watching this thing for 500 days, so we’ve seen 20 or 30 cycles actually of the 16-day period, and it really is like clockwork,” said Canadian Kiyoshi Masui, an assistant professor of physics at MIT’s Kavli Institute for Astrophysics and Space Research and co-author of the paper published in Nature this week. “We only see bursts when we expect to see a burst.”
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Masui said several hundred FRBs have been observed by radio telescopes since the first discovery in 2007, with roughly 20 repeating sources. But until now, there’s never been a pattern to any of them. And that limits astronomers’ understanding of what is actually causing them.
And yes, there’s even been speculation that these signals could be coming from an alien civilization, though others believe it’s unlikely.
The leading hypothesis is that they’re being created by a magnetar, an extremely dense star with a magnetic field that is trillions of times more powerful than that of the sun.
A galactic explosion
Before the new discovery, all the FRBs that have been detected have come from galaxies billions of light years away. But recent bursts from a magnetar in our own galaxy is strengthening the case for FRBs originating from these small but incredibly dense stars.
In a paper published on the pre-print site arXiv.org in May, astronomers reported a strong radio outburst coming from a magnetar called SGR 1935+2154.
Astronomers are, however, hesitant to say that this burst is definitive proof of the FRB source theory.
“One thing that makes the burst from the galactic magnetar different is that it’s still not as bright as the faintest FRBs we detect,” said Scholz, co-author of the Nature paper, who is now an astronomer at the University of Toronto’s Dunlap Institute for Astronomy and Astrophysics. “It’s about 10 to 100 times fainter or less energetic than the FRBs we get … It’s getting close, so it’s tempting to connect these two phenomena together.”
The CHIME/FRB Collaboration, which involves astronomers from around the world though most are Canadian, is constantly searching for these FRBs using the telescope. Since its “first light” on Sept. 7, 2017 — which you can think of as a newborn baby opening his or her eyes for the first time — the telescope has already detected hundreds of FRBs, though astronomers won’t say exactly how many are discovered on a daily basis.
The CHIME telescope, which looks more like a half-pipe than a traditional telescope, is able to search the entire sky for these FRBs, increasing the chances of detection.
While finding only one periodic FRB may seem like an anomaly, Masui said that, when it comes to astrophysics, most things are periodic.
“We see stars orbiting black holes; we see all kinds of things that have periodic behaviour in astrophysics,” he said. “People have been looking for exactly this phenomena ever since FRBs were discovered. We had to wait until now until we had a source that was bright enough and prolific enough to actually see it.”
Astronomers are hopeful that more of these periodic bursts will be found with the collaboration.
Masui is particularly interested in what these bursts can also reveal when it comes to the bigger picture, as the radio waves travel through intergalactic gas and dust.
“It’s not only the astrophysics of this phenomenon, but what they can tell us about the universe as a whole,” Masui said.