MIT astronomers have detected a strange and persistent radio signal from a distant galaxy, which seems to flash with surprising regularity.
The signal is classified as a fast radio burst, or 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 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 nature of this source remains a mystery, although astronomers they suspect that the signal could emanate from a radio pulsar or a magnetarwhich are types of neutron stars: extremely dense, rapidly rotating cores of collapsed giant stars.
“There aren’t many things in the universe that emit strictly periodic signals. 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. Yes we think this new signal could be a magnetar or a pulsar on steroids“, he explained Daniele Michilli, postdoctoral fellow at the Kavli Institute for Astrophysics and Space Research at MIT. The team hopes to detect more periodic signals from this source, which could then 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 how fast the universe is expanding.
The discovery was reported this week in the newspaper Nature and is written by members of the CHIME/FRB collaboration, including MIT co-authors Calvin Leung, Juan Mena-Parra, Kaitlyn Shin and Kiyoshi Masui, as well as Michilliwho also led the discovery first as a researcher at McGill University and then as a postdoctoral fellow at MIT. Since the discovery of the first FRB in 2007, hundreds of similar radio flashes have been detected throughout the universe, most recently by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, a compound interferometric radio telescope four large reflectors. Field of Astrophysical Observatory in British Columbia, Canada.
CHIME continuously monitors the sky as the Earth rotates and is designed to pick up radio waves emitted by hydrogen in the early universe. The telescope is also sensitive to fast radio bursts, and since it began observing the sky in 2018, CHIME detected hundreds of FRBs emanating from different parts of the sky.
The vast majority of FRBs observed to date are single bursts: bursts of ultra-bright radio waves that last a few milliseconds before fading away. 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 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 detected 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, but there were remarkably precise periodic peaks, emitting every split second, boom, boom, boom, like a heartbeat. This is the first time the signal itself is periodic.
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.which appear 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 the radio emissions from our own galactic pulsars and magnetars is that, FRB 20191221A appears to be over a million times brighter. Michilli says the bright flashes may be from a radio pulsar or a distant magnetar which is normally weaker as it spins and for some unknown reason has ejected a train of bright flashes, in a rare window of three seconds that CHIME was fortunately able to detect. Capture.
“CHIME has now detected many FRBs with different propertiessays Michilli. “We have seen some living inside very turbulent clouds, while others seem to be in clean environments. From the properties of this new signal, it can be said that around this source there is a cloud of plasma which must be extremely turbulent.”
Astronomers hope to capture additional bursts of periodic FRB 20191221A, which could help refine your understanding of their origin and of neutron stars in general. “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,” says Michilli. “Future telescopes promise to discover thousands of FRBs per month, and by then we could find many more of these periodic signals.”