Astronomers at MIT and elsewhere have detected a strange radio signal from a distant galaxy that appears to flicker in time with your heartbeat. The signal is a fast radio burst or FRB, an intensely strong burst of radio waves of unknown astrophysical origin, usually lasting a few milliseconds at most. However, the newly detected signal lasts up to three seconds , about 1,000 times longer than the average FRB. It repeats every 0.2 seconds following a pattern similar to that of the heartbeat.
The signal has been named FRB 20191221A and, at the moment, it is the longest FRB, with the clearest periodic pattern. The signal comes from a distant galaxy, located several billion light years from Earth. At the moment, the exact origin of the signal is unknown, although astronomers suspect that it could come from a radio pulsar or a magnetar , both types of neutron stars, collapsed cores of giant stars that are very dense and rotate rapidly. .
“There aren’t 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. “Examples we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce lighthouse-like emission. And we think this new signal could be a magnetar or pulsar on steroids.”
The team of astronomers hopes to detect more signals from this source and use them as an astrophysical clock . The frequency of the outbursts, and how they change as the source moves away from Earth, could be used to measure the rate of expansion of the universe.
The fast radio bursts
Fast Radio Bursts or FRBs were discovered in 2007 . Since then, hundreds of these signals have been detected throughout the universe. The most recent thanks to CHIME , an interferometric radio telescope made up of four large parabolic reflectors located at the Domain Radio Astrophysical Observatory in British Columbia, Canada.
This telescope is continuously observing Earth’s sky and is designed to capture radio waves emitted by hydrogen in the earliest stages of the universe. It is also sensitive to fast radio bursts. Since it became operational in 2018, CHIME has detected hundreds of FRBs coming from different parts of the sky.
The vast majority of FRBs observed so far are point events : ultra-bright bursts of radio waves that last a few milliseconds before fading out. Researchers recently 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 that then repeated every 16 days. This 16-day cycle indicated a periodic pattern of activity, although the signal from the actual radio bursts was random rather than periodic.
On December 21, 2019, the telescope picked up a signal from a potential FRB, which immediately caught the attention of Michilli, who was scanning the incoming data. “It was unusual,” he remembers. “Not only was it very long, lasting about three seconds, but there were periodic spikes that were remarkably precise, making each fraction of a second – thump, thump, thump – sound like a heartbeat.” It is the first time that the signal itself is periodic.”
The discovery has recently been published in the journal Nature .
Referencia: The CHIME/FRB Collaboration., Andersen, B.C., Bandura, K. et al. 2022. Sub-second periodicity in a fast radio burst. Nature. DOI: https://doi.org/10.1038/s41586-022-04841-8
