Astronomers exploring the cosmos have spotted bursts of radio waves from a galaxy far, far away, that repeat every 0.2 seconds in a clear periodic pattern, similar to that of a beating heart.
It appears that a far-off galaxy is flashing with surprising regularity, which is being detected by researchers at MIT and universities across Canada and the United States.
FRBs are intensely powerful bursts of radio waves of unknown astrophysical origin, usually lasting a few milliseconds at most. However, as opposed to the average FRB, this new signal persists for up to three seconds, which researchers say is about a thousand times longer than the average fast radio burst.
The team detected clear periodic patterns of radio waves within this window, similar to a heartbeat.
The signal has been designated FRB 20191221A and is currently the longest-lasting and most periodic FRB found to date.
This signal originates in a galaxy several billion light years away from Earth. There is no clear answer as to what the source could be, but astronomers suspect that the signal could originate from either a radio pulsar or a magnetar, both of which are types of neutron stars.
“There are not many things in the universe that emit strictly periodic signals,” says Daniele Michilli, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research.
Researchers point to the radio pulsars and magnetars in our galaxy as an example, which rotate and emit beams of light similar to lighthouses.
A magnetar or pulsar on steroids could be the source of this new signal, according to scientists.
This source may produce periodic signals that they aim to detect, which could be used to create an astrophysical clock. For example, a measurement of the universe’s expansion rate could be made by looking at the frequency and change of the bursts as the source moves away from Earth.
The discovery is reported today in the journal Nature and authored by CHIME/FRB Collaboration members.
A cosmic heartbeat of unknown origin
FRBs have been discovered across the universe hundreds of times since 2007, the most recent one being detected at British Columbia’s Dominion Radio Astrophysical Observatory by CHIME – an interferometric radio telescope with four large parabolic reflectors.
The CHIME telescope continuously monitors the sky as the Earth rotates, detecting radio waves from hydrogen at the earliest ages of the universe. Since CHIME began observing the sky in 2018, it has been able to detect hundreds of fast radio bursts coming from different directions.
To date, FRBs have largely been one-off events – brief bursts of ultrabright radio waves that blink off after a few milliseconds. Recently, however, researchers have discovered periodic FRBs emitting regular radio waves that appear periodic.
In this signal, four days of random bursts were repeated every 16 days. Despite the fact that the signal of the actual radio bursts was random rather than periodic, this 16-day cycle indicated a systematic pattern of activity.
In December 2019, CHIME detected a potential FRB, which Michilli, who was scanning the incoming data, immediately noticed.
“It was unusual,” he recalls.
“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 signal itself is periodic.”
Brilliant bursts
Michilli and his colleagues found similarities in the patterns of radio bursts from FRB 20191221A with those from radio pulsars and magnetars in our galaxy. A radio pulsar is a neutron star that emits radio waves that pulse as it rotates, whereas a magnetar produces a similar emission due to its extreme magnetic field.
However, this new signal appears to be more than a million times brighter than those coming from our galactic pulsars and magnetars.
During a rare three-second window CHIME was fortunate to catch, a distant radio pulsar or magnetar emitted a train of brilliant bursts that Michilli believes are likely to have originated from.
“CHIME has now detected many FRBs with different properties,” Michilli explains.
“We’ve seen some that live inside clouds that are very turbulent, while others look like they’re in clean environments. 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.”
Additional bursts from periodic FRB 20191221A could provide more information about its source and general neutron stars, the researchers believe.
According to the researchers, the detection raises the question of what is causing this extreme signal that we’ve never seen in the past and how you can use it to study the universe with future telescopes poised to discover thousands of FRBs each month. At this point, we may see more of these periodic signals.
Fast Radio Bursts have given rise to countless theories, including Magnetars, Pulsars, Black Hole Mergers, and even signals from extraterrestrial civilizations.
Further reading at MIT News.
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