They began to search the sky, with focused attention and more powerful tools. And, to their relief, astronomers have now found that, no, FRB 121102 is not the lone example of this intriguing phenomenon.
Read: A spree of signals from across the universe
A Canadian-led team announced Wednesday the discovery of a second repeating FRB. A newly built radio telescope in British Columbia detected six flashes from the same spot in the sky last summer. This FRB, named 180814, appears to originate about 1.5 billion light-years away from Earth, half the distance of the other repeating burst.
The same team has also detected 12 more one-off FRBs, which brings the total number of known flashes to 65. The research, described in a pair of papers in Nature, will provide more clues to one of astronomy’s greatest mysteries.
The two repeating signals have more in common than just their flashy nature. When FRBs arrive at Earth, many appear smeared across a range of frequencies, a sign of their long and bumpy journeys through cosmic material across the universe. This includes FRBs 121102 and 180814. But even though the bursts came from two very different locations, and carved out two very different paths to Earth, their radio waves showed similar distortion patterns.
This particular finding stunned astronomers at a recent conference, where the researchers teased their discovery with a little trick. “They put up images of these bursts, and everyone was like, ‘Okay, that looks familiar,’ and then the person showing it said, ‘Actually, you’ve never seen this before, because they’re from a new repeating FRB,’” said Shami Chatterjee, an astrophysicist at Cornell who studies FRBs and was not involved in the new research. “It looks shockingly similar.”
The similarities suggest the two repeaters may have originated in the same kind of environment. It’s possible that repeating bursts are just one of many classes of FRBs, some yet to be discovered. But with so little information, researchers are far from any definitive conclusions.
“We don’t know what it means yet,” said Ingrid Stairs, an astrophysicist at the University of British Columbia and a member of the research team. “This is our second repeater. I think we need to have a much better sample.”
When the first FRB was discovered in 2007, some astronomers thought the flashes could be errant noise from telescope instruments. The bursts just didn’t seem real. “These things are billions of light-years away,” said Jason Hessels, an astronomer at the University of Amsterdam and ASTRON, the Netherlands Institute for Radio Astronomy, who studies FRBs. “It’s absolutely remarkable that they can still be bright enough to detect on Earth.”
The complicated twisting observed in FRBs suggests they come from extreme environments with strong magnetic fields and high temperatures. Astronomers know of several astrophysical objects that could provide these radio-wave-bending conditions: Supermassive black holes, which can belch streams of radiation in space when they eat matter. Neutron stars, the fast-spinning cores of stars, leftover from spectacular explosions. Magnetars, a certain kind of neutron star, which spin even faster.