It is an extremely strong burst of waves of unknown astrophysical origin, usually lasting a few milliseconds at most.
Astronomers at the Massachusetts Institute of Technology (MIT) and other research centers have detected a strange, persistent radio signal from a distant galaxy that appears to flicker with startling regularity, as reported in the journal “Nature.” The signal is classified as a fast radio burst (FRB), an intensely loud burst of radio waves of unknown astrophysical origin, which typically lasts a few milliseconds at most. However, this new signal persists for up to three seconds, about 1,000 times longer than the average FRB. Within this window, the team detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to that of a beating heart.
Researchers have labeled the FRB signal 20191221A, and it is currently the longest-lasting FRB, with the clearest periodic pattern, detected to date. The source of the signal is in a distant galaxy, several billion light-years from Earth. The exact source remains a mystery, although astronomers suspect the signal could come from a radio pulsar or a magnetar, both types of neutron stars, extremely dense and rapidly rotating collapsed cores of giant stars .
“There aren’t many things in the universe that emit strictly periodic signals,” says Daniele Michilli, a postdoctoral fellow at MIT’s Kavli Institute for Astrophysics and Space Research. The examples we know of in our own galaxy are radio pulsars and magnetars, which spin and produce an emission similar to that of a lighthouse. And we think this new signal could be a magnetar or a pulsar on steroids.”
Waiting for new signs
The team hopes to detect more periodic signals from this source, which could be used as an astrophysical clock. For example, the frequency of explosions and how they change as the source moves away from Earth could be used to measure the rate of expansion of the universe.
The discovery is the work of members of the CHIME/FRB collaboration, including MIT co-authors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin and Kiyoshi Masui of MIT, as well as Michilli, who first led the discovery. as a researcher at McGill University. then as a postdoc at MIT. Since the discovery of the first FRB in 2007, hundreds of similar radio flashes have been detected across the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), an interferometric radio telescope composed of four large reflectors. Dominion Astrophysical Radio Observatory in British Columbia, Canada.
CHIME continuously observes the sky as the Earth rotates and is designed to pick up radio waves emitted by hydrogen in the early stages of the universe. The telescope is also sensitive to fast radio bursts, and since it began observing the sky in 2018, CHIME has detected hundreds of FRBs emanating from different parts of the sky.
The vast majority of FRBs observed to date are punctual: ultra-bright bursts of radio waves that last a few milliseconds before fading away. Researchers recently discovered the first periodic FRB that appeared to emit a regular pattern of radio waves. This signal consisted of a four-day window of random bursts which then repeated every 16 days. This 16-day cycle indicated a periodic pattern of activity, although the signal from actual radio bursts was random rather than periodic.
On December 21, 2019, CHIME picked up a signal from a potential FRB, which immediately caught the attention of Michilli, who was scanning the incoming data. “It was unusual,” he recalls. Not only was it very long, about three seconds long, but there were remarkably precise periodic spikes, emitting every fraction of a second – boom, boom, boom – like a heartbeat. This is the first time that the signal itself has been periodic,” he adds.
Analyzing the radio burst pattern of FRB 20191221A, Michilli and his colleagues found similarities to emissions from radio pulsars and magnetars in our own galaxy. Radio pulsars are neutron stars that emit beams of radio waves that seem to pulsate as the star rotates, while magnetars produce a similar emission due to their extreme magnetic fields.
The main difference between the new signal and radio emissions from our own galactic pulsars and magnetars is that FRB 20191221A appears to be more than a million times brighter. Michilli points out that the flashes of light may have come from a radio pulsar or from a distant magnetar which is normally fainter when rotating and which for some unknown reason has ejected a train of light bursts into a rare window of three seconds than CHIME. fortunately positioned to catch.