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 fast, cosmic flashes from various distant points in the universe have been detected.
Many FRBs emit super-bright radio waves that last for a few milliseconds at most before disappearing completely, and about 10% of these are known to have repetitions and patterns.
One source used to detect them is a radio telescope called the Canadian Hydrogen Density Mapping Experiment, or CHIME, located at the Dominion Radio Astrophysical Observatory in British Columbia, Canada.
In operation since 2018, this telescope is constantly observing the sky and is sensitive to radio waves emitted by distant hydrogen in the universe, in addition to fast radio bursts.
Astronomers using CHIME noticed something that immediately caught their attention on December 21, 2019: a fast radio burst that was “strange in many ways,” according to postdoctoral researcher Daniele Michilli. At the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Studies.
The signal, named FRB 20191221A, lasted up to three seconds – about 1000 times longer than typical fast radio bursts.
Michilli was monitoring data from CHIME when the explosion occurred. The signal is the longest sustained fast radio burst to date.
“It was unusual,” Michilli said. “Not only was it very long, it lasted about three seconds, but there were periodic peaks that were remarkably precise, radiating every fraction of a second — boom, boom, boom — like a heartbeat. This is the first time the signal itself has been periodic.”
While FRB 20191221A has yet to recur, “the signal consists of consecutive peaks that we found to be separated by ~0.2 seconds,” he said in an email.
an unknown source
Michilli said the research team did not know exactly the galaxy where the explosion occurred, and that even an estimate of a billion light-years away was “pretty uncertain.” While CHIME is ready to look for bursts of radio waves, it’s not that good at finding starting points.
However, CHIME is being developed through a project where additional telescopes currently under construction will observe together and triangulate radio bursts to specific galaxies, he said.
But the signal contains clues as to where it’s coming from and what might be causing it.
“CHIME has now detected many FRBs with different properties,” Michilli said. Said. “We’ve seen some living in clouds that are very turbulent, while others appear to be in clean environments. From the properties of this new signal, we can say that there is a cloud of plasma around this source that should be extremely turbulent.”
When the researchers analyzed FRB 20191221A, the signal resembled emissions from two different neutron stars, or dense remnants after a giant star called radio pulsars and magnetars died.
Magnetars are neutron stars with incredibly strong magnetic fields, while radio pulsars emit radio waves that appear to vibrate as the neutron star rotates. Both star objects generate a signal similar to a flashing beam from a lighthouse.
The fast radio burst appears a million times brighter than these emissions. “We think this new signal could be a magnetar or a pulsar on steroids,” Michilli said. Said.
The research team will continue to use CHIME to monitor the sky for more signals from this radio burst and others with a similar, periodic signal. The frequency of radio waves and how they change can be used to help astronomers learn more about the expansion rate of the universe.
“This detection raises the question of what could be causing this extreme signal that we’ve never seen before and how we can use this signal to study the universe,” Michilli said. Said. “The telescopes of the future promise to discover thousands of FRBs per month, and at this point we can find most of these periodic signals.”
