Rapid radio bursts, or FRBs, are intense bursts of radio waves of up to milliseconds from an unknown source. The first FRBs were discovered in 2007, and since then, hundreds of these cosmic flashes have been detected coming from different and distant points throughout the universe.
Many FRBs emit ultra-bright radio waves that last only a few milliseconds before disappearing completely, and about 10% of them are known to repeat and have patterns.
One of the sources used to find it is a radio telescope called the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, at the Dominion Astrophysics Observatory in British Columbia, Canada.
This telescope, which has been in operation since 2018, is constantly observing the sky, and in addition to its fast radio bursts, it is sensitive to radio waves emitted by hydrogen deep in the universe.
Astronomers using CHIME discovered something on December 21, 2019, that immediately caught their attention: a fast radio burst that was “in many ways odd,” according to Danielle Mitchell, a postdoctoral researcher. di Kavli Institute for Astrophysics and Space Research di Massachusetts Institute of Technology.
The signal, called FRB 20191221A, lasted up to three seconds — about 1,000 times longer than a typical fast radio burst.
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Michelli was monitoring data received from CHIME, when the explosion occurred. The signal is the most durable fast radio wave to date.
“It was amazing,” said Micheli. “It wasn’t very long, and lasted about three seconds, but there was a very accurate periodic peak, with every millisecond—boom, boom, boom—radiating like a heartbeat. This is the first time the signal itself has cycled. . . “
While FRB 20191221A has not replicated, “the signal is formed by a series of consecutive peaks that we found separated by about 0.2 seconds,” he said in an email.
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Micheli said the research team didn’t know exactly which galaxy the explosion came from, and even the estimated distance of up to a billion light years was “highly uncertain”. While CHIME is ready to search for a collection of radio waves, they are not very good at pinpointing their point of origin.
However, CHIME is being developed through a project in which additional telescopes, currently under construction, will co-monitor and be able to triangulate radio bursts from specific galaxies, he said.
But the signal contains clues about where it’s coming from and what might be causing it.
“CHIME has now detected many FRBs with different characteristics,” Micheli said. “We have seen some people living in very turbulent clouds, while others appear to be in a clean environment. From the characteristics of this new signal, we can tell that in the vicinity of this source, there is a plasma cloud that must be very turbulent.”
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When the researchers analyzed FRB 20191221A, the signal was similar to emissions from two different types of neutron stars, or solid remnants after the death of giant stars, called radios and magnetic pulsars.
Magnetars are neutron stars with very strong magnetic fields, while radio pulsars emit radio waves that appear to pulsate as the neutron star rotates. The two stellar objects make a signal similar to the beam of light from a lighthouse.
The fast radio bursts appear to be a million times brighter than this emission. “We think this new signal could be a magnetar or pulsar on doping,” Micheli 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 similar periodic signals. The frequency of radio waves and how they change can be used to help astronomers learn more about the rate at which the universe is expanding.
“This discovery raises questions about what could be causing these extreme signals we’ve never seen before, and how we can use these signals to study the universe,” Micheli said. “Future telescopes promise to detect thousands of FRBs per month, where we can find more of these periodic signals.”
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