FRBs: Another Repeating Radio Signal From Deep Space Has Been Discovered

A second repeating radio signal has been detected from deep space, scientists announced. The signal—known as a fast radio burst, or FRB—was found to repeat six times and appeared to originate from a distance of 1.5 billion light-years away.

FRBs are, as the name suggests, radio bursts that last only a few milliseconds. Because they are so short-lived, they are often only discovered in data, long after the burst occurred. This has made tracing their origin to understand their source extremely challenging.

Read more: What are FRBs? Mystery repeating signals from deep space explained (sort of)

The first FRBs were discovered almost two decades ago. Since then dozens of mystery radio signals have been identified by scientists, and telescopes across the world are now being used to home in on their source.

Because most FRBs are one-off events, scientists initially thought they were probably produced by some cataclysmic cosmic event—potentially the collision of two neutron stars, or the collapse of a black hole, for example. However, in 2016 scientists discovered something that made FRBs even more perplexing—a signal that repeated.

This FRB, known as FRB 121102, was found to repeat 10 times and, using this data, scientists were able to track it back to a dwarf galaxy 3 billion light-years away. In 2017, researchers said 15 more bursts had been identified coming from FRB 121102. This discovery meant—in the case of FRB 121102 at least—that a one-off cataclysmic event could not be the cause.

In a study published in Nature, scientists with the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Collaboration have now reported the discovery of another repeating FRB. Scientists found the burst, called FRB 180814.J0422+73, repeated six times. It appeared to be coming from a distance of 1.5 billion light-years away—half that of FRB 121102.

The researchers say the new repeating radio signal shares certain features with the FRB 121102, indicating the two bursts have "similar emission mechanisms and/or propagation effects," the team wrote. They say that because this second repeater was found relatively easily, there are likely to be a "substantial population of repeating FRBs."

"Until now, there was only one known repeating FRB," Ingrid Stairs, one of the study authors and member of the CHIME team, said in a statement. "Knowing that there is another suggests that there could be more out there. And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles—where they're from and what causes them."

Andrew Siemion, an astrophysicist and director of the Berkeley SETI Research Center, told Newsweek the latest findings represent an incredible discovery. "Up until this point FRB 121102 has been a truly singular object," he said. "It is amazing how much similarity in spectral and temporal behavior there is between this second repeater and 121102, including very limited spectral extent and drifting emission. The localization of 180814.J0422+73 will certainly improve in the coming months, which will provide opportunities to follow this source up at higher frequencies as was done with 121102. It will be particularly interesting to see whether it emits at higher frequencies, and if so how it compares with 121102.

"Kudos to the crack team of scientists and engineers at CHIME that led this remarkable discovery. This clearly demonstrates the power of exploring new parameter space in frequency and field-of-view. Moreover, CHIME has opened a new window on the FRB population, a window that will be critical to unraveling the mystery of these enigmatic objects."

Astrophysicist Ryan Shannon, from Australia's Swinburne University, recently discovered another set of FRBs. Commenting on the new study, he said it was exciting to see another repeating FRB. "It is great to see the second repeating burst source," he told Newsweek. "It's early days, but I'll be excited when it is pinpointed, to see if it resides in an environment like the first repeating FRB.

"I'm really excited for the next year, and I think we'll get a lot closer to understanding what they [FRBs] are—or at least what they aren't... To solve the mystery of FRBs we need to find more and figure out where they come from. The [scientific] community is poised to do that this year."

More Single Bursts Discovered

Along with the repeating burst, researchers also detected 12 other FRBs during their survey in July and August last year. Their other findings are detailed in another Nature paper. What was interesting about these bursts is that they were found at the lowest frequency the telescope they used was capable of detecting. Previously, FRBs were found at frequencies of around 1,400 megahertz. The new bursts were all between 400 MHz and 800 MHz. This discovery puts some constraints on what could have produced the bursts.

Tom Landecker, another CHIME team member, explained: "[We now know] the sources can produce low-frequency radio waves and those low-frequency waves can escape their environment, and are not too scattered to be detected by the time they reach Earth. That tells us something about the environments and the sources. We haven't solved the problem, but it's several more pieces in the puzzle."