Cosmic ‘heartbeat’ detected in fast radio burst billions of light-years from Earth
The new FRB is the longest lasting with the clearest pattern known.
Astronomers have detected a new fast radio burst, or FRB, from a galaxy far, far away. The new FRB is currently the longest lasting with the clearest periodic pattern ever observed.
FRBS are strong pulses of electromagnetic radiation in the radio-frequency end of the spectrum. The first FRB, known as the Lorimer burst, was detected in 2007, but their exact astrophysical origins still remain mysteries.
Typically, fast radio bursts last a few milliseconds at most, and either go quiet or, very rarely, repeat somewhat periodically. This new signal, however, is about three seconds long – about a thousand times longer than the average FRB – and contains a clear periodic pattern repeating every 0.2 seconds.
Labelled FRB 20191221A, the burst’s source is in a galaxy several billion light-years from Earth and is theorised to be a neutron star like a radio pulsar or magnetar. The finding is described in a paper published in Nature.
“There are not many things in the universe that emit strictly periodic signals,” says co-author Daniele Michilli, a postdoc in MIT’S Kavli Institute for Astrophysics and Space Research, US.
“Examples that we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beamed emission similar to a lighthouse. And we think this new signal could be a magnetar or pulsar on steroids.”
FRBS have been detected across the universe. One instrument that has recently been finding radio bursts is the interferometric radio telescope Canadian Hydrogen Intensity Mapping Experiment, or CHIME.
As Earth has rotated, CHIME – which began observations in 2018 – has picked up radio waves emitted by hydrogen in the early universe as well as hundreds of FRBS.
Most of the bursts CHIME has found are fleeting and random in their construction. But, like a stethoscope on the universe’s rib cage, on 21 December 2019 CHIME found a cosmic pulse.
“It was unusual,” Michilli says. “Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second – boom, boom, boom – like a heartbeat. This is the first time the FRB signal itself is periodic.”
The team analysed the signal and found similarities with pulsars and magnetars in our own galaxy – only the pulses from FRB 20191221A are more than a million times brighter. The researchers believe this means that the FRB may have come from a neutron star that is normally much less bright but ejected a series of magnificent bursts.
“From the properties of this new signal, we can say that around this source, there’s a cloud of plasma that must be extremely turbulent,” Michilli says.
If more pulses from FRB 20191221A can be seen in the future, it may help the researchers understand the source of the burst as well as neutron stars in general.