Fast radio bursts, or FRBs, are intense, millisecond-long bursts of radio waves of unknown origin. The first FRB was discovered in 2007, and since then, hundreds of these rapid, cosmic flashes have been detected coming from various distant points across the universe.
Many FRBs emit super bright radio waves that last only a few milliseconds before disappearing completely, and about 10% of them are known to repeat and have patterns.
The telescope, operational since 2018, continuously monitors the sky and is sensitive to radio waves emitted by distant hydrogen in the universe, in addition to fast radio bursts.
On December 21, 2019, astronomers using CHIME spotted something that immediately caught their attention: a fast radio burst that was “strange in many ways,” says postdoctoral researcher Daniel Micheli. at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research.
The signal, named FRB 20191221A, lasted up to three seconds — about 1,000 times longer than typical fast radio bursts.
Micheli was monitoring data from CHIME when the explosion occurred. The signal is the fastest radio burst to date.
“It’s extraordinary,” Micheli said. “Not only was it very long, lasting about three seconds, but there were periodic peaks that emitted each fraction of a second — boom, boom, boom — like a heartbeat. This is the first time the signal itself is periodic.”
Although FRB 20191221A has yet to repeat, “the signal is composed of a train of consecutive peaks that we detect are separated by ~0.2 seconds,” he said in an email.
Unknown source
The exact group of galaxies where the burst originated is unknown, and even a distance estimate of a billion light-years is “highly uncertain,” Michilli said. Although CHIME is primed for searching for bursts of radio waves, it is not particularly good at locating their points of origin.
However, CHIME is being enhanced by additional telescopes currently under construction that will monitor together and triangulate radio bursts to specific galaxies, he said.
But that signal contains clues as to where it came from and what caused it.
“CHIME has now detected many FRBs with different properties,” said Michelli. “We’ve seen some that live inside very turbulent clouds, while others seem to be in a clean environment. From the properties of this new signal, we can say that there must be a plasma cloud around this source. Very turbulent.”
When researchers examined FRB 20191221A, the signal resembled emissions from two different types of neutron stars, or radio pulsars, and the dense remnants of a massive star after it died, called magnetars.
Magnetos are neutron stars with incredibly powerful magnetic fields, while radio pulsars emit pulsating radio waves as the neutron star spins. Both stellar objects produce a signal similar to a beam of light from a lighthouse.
A fast radio burst appears a million times brighter than these emissions. “We think this new signal could be a magnet or pulsar on steroids,” Michili said.
The research team will continue to use CHIME to monitor the sky for more signals from this radio burst, as well as others with periodic signals. The frequency of radio waves and how they change can help astronomers learn more about the rate of expansion of the universe.
“This finding raises the question of what could be causing this intense signal that we’ve never seen before, and how we can use this signal to study the universe,” Micheli said. “Future telescopes promise to find thousands of FRPs a month, during which time we can see many of these periodic signals.”
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