Astronomers detect a radio 'heartbeat' billions of light-years from Earth

Astronomers at MIT and other locations have discovered a peculiar and enduring radio signal coming from a distant galaxy that appears to be flashing surprisingly often.

The signal is categorized as a fast radio burst (FRB), which is a brief but extremely powerful burst of radio waves with an unknown astrophysical origin. However, compared to the typical FRB, this novel signal lasts up to three seconds, or 1,000 times longer. The scientists discovered radio wave bursts inside this window that have a distinct periodic rhythm and reoccur every 0.2 seconds, like a heartbeat.

The signal, FRB 20191221A, was identified by the researchers as the longest-lasting FRB to date and having the most distinct periodic pattern.

Several billion light-years away from Earth, in a far-off galaxy, is where the signal's source is located. Astronomers believe the signal may have come from either a radio pulsar or a magnetar, two different forms of neutron stars that are incredibly compact and fast spinning collapsed cores of big stars. However, the precise nature of that source is yet unknown.

According to Daniele Michilli, a postdoc at MIT's Kavli Institute for Astrophysics and Space Research, "There are not many entities in the cosmos that generate exactly periodic signals." "Examples of rotating objects that emit a beam of light like to a lighthouse are radio pulsars and magnetars, which we are aware of in our own galaxy. Furthermore, we believe that this new signal may be an enhanced magnetar or pulsar."

In order to use this source as an astrophysical clock, the team wants to find more periodic signals from it. For instance, the velocity of the universe's expansion might be gauged by the frequency of the bursts and how they alter as the source travels away from Earth.

Members of the CHIME/FRB Collaboration, including Calvin Leung, Juan Mena-Parra, Kaitlyn Shin, and Kiyoshi Masui at MIT, along with Michilli, who led the discovery first as a researcher at McGill University and then as a postdoc at MIT, are the authors of the discovery, which was published today in the journal Nature.

Boing, boing, boing

Since the first FRB was found in 2007, hundreds of comparable radio flashes have been found throughout the cosmos. The most recent discovery was made by the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, an interferometric radio telescope made up of four sizable parabolic reflectors at the Dominion Radio Astrophysical Observatory in British Columbia, Canada.

CHIME, which is built to detect radio waves released by hydrogen in the very early phases of the cosmos, continually scans the sky as the Earth spins. The telescope is also capable of picking up fast radio bursts, and since it started scanning the sky in 2018, CHIME has picked up hundreds of FRBs coming from various locations.

The great majority of FRBs that have been seen so far are one-offs, which are ultrabright radio wave bursts that last just a few milliseconds before disappearing. Recently, scientists made the first observation of a periodic FRB that seemed to generate a predictable pattern of radio waves. A four-day span of erratic bursts that then repeated every 16 days made up this signal. Despite the fact that the signal of the actual radio bursts was random rather than periodic, this 16-day cycle showed a periodic pattern of activity.

On December 21, 2019, CHIME detected a probable FRB signal, which quickly caught Michilli's eye as she was examining the incoming data.

It seemed strange, he remembers. "It was around three seconds long and extremely lengthy, but it also had periodic peaks that were astonishingly exact and released every fraction of a second — boom, boom, boom — much like a heartbeat. The signal itself is periodic for the first time at this point."

dazzling flashes

Michilli and his colleagues discovered parallels between the pattern of radio bursts from FRB 20191221A and those coming from radio pulsars and magnetars in our own galaxy. While magnetars create a comparable emission because of their strong magnetic fields, radio pulsars release beams of radio waves that appear to pulse as the star rotates.

FRB 20191221A looks to be more than a million times brighter than radio emissions from our own galactic pulsars and magnetars, which is the fundamental distinction between the new signal and those from those objects. According to Michilli, the light flashes may be the result of a distant radio pulsar or magnetar that, for some reason unknown to scientists, unleashed a series of spectacular bursts within a brief three-second window that CHIME was fortunate enough to see.

According to Michilli, "CHIME has now identified several FRBs with various characteristics." "Some of the creatures we've observed dwell in extremely chaotic clouds, while others appear to be in pristine settings. We may infer from the characteristics of this new signal that the plasma cloud around this source must be quite turbulent."

The periodic FRB 20191221A is expected to produce more bursts, which might help astronomers better understand neutron stars in general and its source.

According to Michilli, "This discovery begs the issue of what may be the origin of such an extreme signal that we have never seen before, and how can we utilize this signal to explore the cosmos." "Future telescopes promise to locate thousands of FRBs a month, and at that time we may uncover many more of these periodic signals," the statement continued.

The Canada Foundation for Innovation provided some funding for this study.

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Materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu.