In April, a group of astronomers spotted a short, powerful blast of radio waves coming from outer space and then successfully found where it was coming from: a powerful object within our own galaxy. It’s the first time scientists have been able to pinpoint these mysterious radio waves coming from inside the Milky Way, making them the closest of their kind that we’ve ever seen.
The radio waves — known as fast radio bursts, or FRBs — seem to have sprouted from an incredibly powerful “zombie” star lurking in our galaxy, according to three papers published in the journal Nature. Called a neutron star, the object is a super dense leftover that forms when a massive star, bigger than our own Sun, collapses in on itself. But this neutron star is what’s known as a magnetar. It hosts an incredibly powerful magnetic field that stores mind-boggling amounts of energy, capable of distorting the shapes of atoms.
Tracking down the source of this FRB is a huge moment for astronomers
Tracking down the source of this FRB is a huge moment for astronomers, who are eager to figure out how these mystifying radio flashes come to be. FRBs are thought to appear once every second in the night sky, flaring for just a few milliseconds at a time. But we’ve only seen a tiny fraction of these phenomena at play, and all of the bursts we have seen have apparently stemmed from outside our galaxy, with some located billions of light-years away. That’s made it difficult to figure out exactly where they’re coming from. “They’re these very mysterious signals, and we don’t have a really good idea of what’s producing them or what the physics is behind it,” Kiyoshi Masui, an assistant professor of physics at MIT who worked on the discovery, tells The Verge.
Now with this discovery, astronomers have a much closer source to work with. The magnetar is located just 30,000 light-years away — in our own backyard, cosmically speaking. And it points to a solid connection between magnetars and these dynamic space radio waves. “This is the missing link,” Masui says. “Now we’ve seen a fast radio burst coming from a magnetar, so it proves that at least some fraction of fast radio bursts we see in the universe come from magnetars.”
Scientists have been trying to hunt down the origins of FRBs ever since the first one was detected in 2007. But because FRBs are so fleeting, spotting them has often required a combination of looking in the right place at the right time with the right equipment. Astronomers got lucky when they found a few FRBs that seem to repeat, flashing over and over again in the same part of the sky. These recurrent bursts helped scientists locate the galaxies where these radio waves originate. Still, it’s unclear exactly which objects inside these galaxies are producing the FRBs.
“When I looked at the data for the first time I froze.”
That’s why this discovery is so crucial. Two different observatories in North America — CHIME in Canada and STARE2 in the United States — spotted this FRB coming from the same part of the sky, strengthening the credibility of the signal. The FRB was also incredibly bright. In fact, a regular cellphone 4G LTE receiver would have been able to pick up the signal coming from halfway across the galaxy, according to Christopher Bochenek, a graduate student in astronomy at Caltech who led the STARE2 discovery team.
“When I looked at the data for the first time I froze and was basically paralyzed with excitement,” Bochenek said during a press call.
The timing and location of the flash lined up with another cosmic event happening nearby. Just a few days before the FRB was detected, astronomers noticed that a known magnetar had gotten pretty hyperactive in the sky, sending out X-rays and gamma rays. After analyzing the data from the FRB, astronomers at both CHIME and STARE2 confirmed that the radio waves had coincided with a particularly large burst of X-rays from the magnetar. The discovery already made waves in the astronomy community earlier this year, with early scientific reports of the connection posted online and covered in the media. The researchers’ results have now been reviewed by other scientists and are being formally presented in the journal Nature this week.
The mechanics at play are still not fully understood
Magnetars could make a pretty great origin story for many FRBs. Scientists have suspected these dead magnetic stars might be behind radio flashes for a while, as they are jam-packed full of energy and prone to sending out bursts of different types of light for fractions of a second. “This discovery, therefore, paints a picture that some and perhaps most — given how common these events are in the universe — fast radio bursts from other galaxies originate from magnetars,” Bochenek said.
But astronomers aren’t proclaiming the mystery behind FRBs solved just yet. For one thing, astronomers continued to monitor the magnetar as it burped up more X-rays and gamma rays, but those follow-up events didn’t match up with any significant radio wave bursts. Plus, this burst was still relatively weak compared to other FRBs we’ve seen. It’s actually 1,000 times weaker than the weakest FRB spotted coming from outside our galaxy. So the mechanics at play are still not fully understood.
The good news is astronomers have some pretty good suspects to probe. Not only can they continue to study this one magnetar, but there are around 30 other known magnetars that will probably get a lot of extra attention now. And astronomers might focus on finding FRBs in other galaxies where magnetars are suspected to be. That could give us a better understanding if this one event was an offshoot — or the final piece of the FRB puzzle.
“We still don’t really know exactly how lucky we got,” Bochenek says. “This could be like a once in five year thing. Or there could be a few of these things that happen every year. But with more events, we would be able to tell exactly how lucky we... were.”