Astronomers have detected a persistent radio signal from a distant galaxy that appears to blink with surprising regularity. Called FRB 20191221A, this fast radio burst, or FRB, is currently the longest-lasting FRB, with the clearest periodic pattern discovered to date. Pictured is the large CHIME radio telescope that caught the FRB. Credit: CHIME, with background edited by MIT News
Astronomers at MIT and elsewhere have detected a strange and persistent radio signal from a distant galaxy that appears to blink with surprising regularity.
The signal is classified as a Fast Radio Burst, or FRB – an intensely strong burst of radio waves of unknown astrophysical origin that typically lasts a few milliseconds at most. However, this new signal lasts up to three seconds, about 1,000 times longer than the average FRB. In this window, the team found bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to a beating heart.
Researchers have labeled the signal FRB 20191221A, and it is currently the longest-lasting FRB, with the clearest periodic pattern found to date.
The source of the signal is located in a distant galaxy, several billion light years from Earth. Exactly what that source might be remains a mystery, although astronomers suspect that the signal could originate from either a radio pulsar or a magnetar, both of which are types of neutron stars — the extremely dense, fast-spinning collapsed cores of giant stars.
“There aren’t many things in the universe that emit strictly periodic signals,” says Daniele Micilli, a postdoctoral fellow at MIT’s Kavli Institute for Astrophysics and Space Studies. “Examples we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beacon-like beam. And we think this new signal could be a magnetar or a pulsar on steroids.”
The team hopes to detect more periodic signals from this source, which can then be used as an astrophysical clock. For example, the frequency of bursts and how they change as the source moves away from Earth can be used to measure the rate at which the universe is expanding.
The discovery is reported today in the journal Natureand is authored by members of the CHIME/FRB Collaboration, including MIT coauthors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin, and Kiyoshi Masui of MIT, along with Michilli, who led the discovery first as a researcher at McGill University and then as a postdoc at MIT.
“Boom, Boom, Boom”
Since the first FRB was detected in 2007, hundreds of similar radio flashes have been detected in the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, an interferometric radio telescope consisting of four large parabolic reflectors located at the Dominion Radio Astrophysical 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 earliest 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 emitted from different parts of the sky.
Most FRBs observed so far are one-shots—ultrabright bursts of radio waves that last a few milliseconds before fading. Recently, researchers discovered the first periodic FRB that appeared to emit a regular pattern of radio waves. This signal consisted of a four-day window of occasional outbursts, which then recurred every 16 days. This 16-day cycle shows a periodic pattern of activity, although the signal from the actual radio bursts is more random than periodic.
On December 21, 2019, CHIME picked up a signal of a potential FRB, which immediately caught the attention of Michili, who was scanning the incoming data.
“It was unusual,” he recalls. “Not only was it very long, about three seconds long, but there were periodic spikes that were remarkably precise, emitting every fraction of a second – boom, boom, boom – like a heartbeat. This is the first time that the signal itself is periodic.”
Brilliant bursts
In analyzing the pattern of radio bursts in FRB 20191221A, Michili and his colleagues found similarities with the emission from radio pulsars and magnetars in our own galaxy. Radio pulsars are neutron stars that emit beams of radio waves that appear to pulsate as the star rotates, while similar emission is produced by magnetars due to their extreme magnetic fields.
The main difference between the new signal and the radio emissions from our galactic pulsars and magnetars is that FRB 20191221A appears more than a million times brighter. Michili says the flashes of light may originate from a distant radio pulsar or magnetar, which is usually fainter as it spins and for some unknown reason threw off a series of brilliant bursts in a rare three-second window that CHIME was fortunately able to caught.
“CHIME has already detected many FRBs with different properties,” says Michili. “We’ve seen some that live in clouds that are very turbulent, while others appear to be in a clear environment. From the properties of this new signal, we can tell that there is a cloud of plasma around this source that must be extremely turbulent.”
Astronomers hope to catch additional bursts from the periodic FRB 20191221A, which could help refine their understanding of its source and neutron stars in general.
“This discovery raises the question of what could be causing this extreme signal that we have never seen before, and how we can use this signal to study the universe,” says Michili. “Future telescopes promise to detect thousands of FRBs per month, and at this point we may detect many more of these periodic signals.”
Fast radio bursts have been shown to involve lower frequency radio waves than previously detected More information: Daniele Michilli, Sub-second periodicity in a fast radio burst, Nature (2022). DOI: 10.1038/s41586-022-04841-8. www.nature.com/articles/s41586-022-04841-8 Courtesy of MIT
Citation: Astronomers detect radio ‘heartbeat’ billions of light years from Earth (2022 July 13) Retrieved July 13, 2022 by
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