Astronomers have traced the signal of an enigmatic repeating fast radio burst for only the second time – and it’s in a spiral galaxy similar to our own, not so far away.
Fast radio bursts, or FRBs, are millisecond-long bursts of radio waves in space. Individual radio bursts emit once and don’t repeat. Repeating fast radio bursts are known to send out short energetic radio waves multiple times.
Multiple individual fast radio bursts in past years have been traced back to their sources in other galaxies, although those have yet to shed light on what created them.
But this newly discovered repeating FRB has a different source from the first one that was found in 2019, deepening the mystery of how these radio waves are created.
Wonders of the universe
The source of the new repeating FRB, known as 180916.J0158+65, was observed by the global effort of eight ground-based telescopes, which pinpointed the location in a galaxy half a billion light-years from Earth. While that sounds incredibly distant, it’s seven times closer than the other repeating radio burst and more than 10 times closer than non-repeating FRBs that have been traced.
“The FRB is among the closest yet seen, and we even speculated that it could be a more conventional object in the outskirts of our own galaxy,” said Mohit Bhardwaj, study co-author and McGill University doctoral student. “However, the observation proved that it’s in a relatively nearby galaxy, making it still a puzzling FRB but close enough to now study using many other telescopes.”
The study published Monday in the journal Nature, and its findings were presented at the 235th annual meeting of the American Astronomical Society in Honolulu.
The first repeating fast radio burst traced, FRB 121102, linked back to a small dwarf galaxy containing stars and metals.
“The multiple flashes that we witnessed in the first repeating FRB arose from very particular and extreme conditions inside a very tiny [dwarf] galaxy,” said Benito Marcote, lead study author from the Joint Institute for VLBI in Europe, which turns a global network of telescopes into a single observatory. “This discovery represented the first piece of the puzzle but it also raised more questions than it solved, such as whether there was a fundamental difference between repeating and non-repeating FRBs. Now, we have localized a second repeating FRB, which challenges our previous ideas on what the source of these bursts could be.”
On June 19, 2019, the joint institute tuned in to the repeating fast radio burst, which was initially discovered by Canada’s CHIME telescope in 2018. Over five hours, the telescopes detected four bursts that lasted less than two thousandths of a second.
They used a technique called Very Long Baseline Interferometry to combine the power of the telescopes and use them as one to pinpoint the FRB’s location to a region that was seven light-years across. The astronomers compared that ability to someone standing on Earth being able to recognize someone on the moon.
Not only does this new repeating fast radio burst differ from the other traced repeating one, but from all fast radio bursts ever traced.
“The differences between repeating and non-repeating fast radio bursts are thus less clear, and we think that these events may not be linked to a particular type of galaxy or environment,” said Kenzie Nimmo, study co-author and PhD student at the University of Amsterdam. “It may be that FRBs are produced in a large zoo of locations across the universe and just require some specific conditions to be visible.”
The repeating fast radio burst was traced to one of the spiral arms of a Milky Way-esque galaxy. It was also within a star-forming region of the arm, the researchers said.
Learning more about the host galaxy of the burst can tell astronomers about the environment from which these originate and, ultimately, unravel the big mystery of what creates them. Given the fact that this one is closer than the others, astronomers will observe it more in the future.
Understanding fast radio bursts can also help astronomers learn more about the universe itself. The more bursts they can trace, the better they may be able to use the signals to map how matter is distributed across the universe.