Astronomers detect ‘strange’ radio signal from faraway galaxy
Image credit: Photo courtesy of CHIME, with background edited by MIT News
MIT astronomers have detected a strange and persistent radio signal from a galaxy several billion light years from Earth that could be used to measure the rate at which the universe is expanding.
Astronomers at the Massachusetts Institute of Technology (MIT) have detected a fast radio burst (FRB) coming from a distant galaxy that appears to be flashing with surprising regularity.
These types of signals are usually short-lasting. However, this new signal persists for up to three seconds, about 1,000 times longer than the average FRB. Within this window, the MIT team detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to a beating heart.
The new signal, labelled 'FRB 20191221A', is the longest-lasting FRB, with the clearest periodic pattern detected to date.
The origin of the radio signal remains a mystery, although researchers have been able to trace it back to a galaxy located several billion light-years from Earth.
“There are not many things in the universe that emit strictly periodic signals,” said Daniele Michilli, a member of the MIT research team. "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.”
The team hopes to detect more periodic signals from this source, which could then be used as an astrophysical clock. More significantly, the frequency and trajectory of the bursts could be used to measure the rate at which the universe is expanding.
The discovery has been published today in the journal Nature.
Since the first FRB was discovered 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 consisting of four large parabolic reflectors.
CHIME is designed to pick up radio waves emitted by hydrogen in the very earliest stages of the universe. The telescope also happens to be sensitive to fast radio bursts and has identified hundreds of new FRBs.
The vast majority of FRBs observed to date are one-offs. However, FRB 20191221A, first picked up in December 21 2019, was not. This signal consisted of a four-day window of random bursts that were then repeated every 16 days.
“It was unusual,” Michilli said. “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.”
After analysing FRB 20191221A’s radio bursts, Michilli and his colleagues found similarities with emissions from radio pulsars and magnetars in our own galaxy, except for the fact that FRB 20191221A appeared to be more than a million times brighter.
“CHIME has now detected many FRBs with different properties,” Michilli says. “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.”
The astronomers hope to catch additional bursts from the periodic FRB 20191221A, which can help to refine their understanding of its source and of neutron stars in general.
The James Webb Space Telescope, which last night revealed the "deepest" image of the universe so far, might help in this endeavour, just as its predecessor the Hubble telescope once did, and reveal more clues about the origins of the universe.
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