Scientists Detect 'Strange, Persistent' Radio Signal From Distant Galaxy

Scientists have discovered a "strange and persistent" radio signal from a far-off galaxy that sounded like a heartbeat. Astronomers at the Massachusetts Institute of Technology and elsewhere detected the signal, which is classified as a fast radio burst, or FRB — but lasted much longer.

A typical FRB, which is a strong burst of radio waves, lasts a few milliseconds. The new signal lasted up to three seconds – about 1,000 times longer than average, according to a news release. The astrophysical origins of FRBs are unknown.

The signal repeated over .02 seconds in a clear pattern, almost like a heartbeat. 

"It was unusual," said Daniele Michilli, a postdoc in MIT's Kavli Institute for Astrophysics and Space Research. "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."

The signal came from a distant galaxy, several billion light-years from Earth. Researchers from MIT and McGill University in Canada, who published a study on the signal, have named it FRB 20191221A. It is currently the longest-lasting FRB with the clearest periodic pattern detected to date.

The first FRB was discovered in 2007 and hundreds of similar radio flashes have been detected in space since. 

The Canadian Hydrogen Intensity Mapping Experiment, or CHIME, is an interferometric radio telescope that continuously observes the sky and is sensitive to fast radio bursts. 

Most FRBs are one-offs and last a few milliseconds before ending. But a signal that repeated every 16 days was recently discovered, although the signal was more random than periodic. 

But in December 2019, CHIME detected the periodic, heartbeat-like signal. Michilli was scanning the incoming data at the time. "There are not many things in the universe that emit strictly periodic signals," Michilli said.

The source of the new FRB remains a mystery, but scientists think it could emanate from a radio pulsar or magnetar, which are neutron stars. These are dense, rapidly spinning collapsed cores of giant stars. 

"CHIME has now detected many FRBs with different properties," said Michilli. "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."

They hope to catch more bursts from FRB 20191221A. The detection could help them as they study the universe and neutron stars.

"This detection raises the question of what could cause this extreme signal that we've never seen before, and how can we use this signal to study the universe," said Michilli. "Future telescopes promise to discover thousands of FRBs a month, and at that point we may find many more of these periodic signals."

More periodic signals from this source could be used as an astrophysical clock. "For instance, the frequency of the bursts, and how they change as the source moves away from Earth, could be used to measure the rate at which the universe is expanding," the press release reads.

First published on July 15, 2022 / 10:00 AM

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