Scientists have spotted a “strange and persistent” radio signal from a galaxy far, far away that sounded like a heartbeat. Astronomers at the Massachusetts Institute of Technology and elsewhere spotted 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, according to a press release — about 1,000 times longer than average. The astrophysical origins of FRBs are unknown.
The signal repeated over 0.02 seconds in a clear pattern, almost like a heartbeat.
“It was unusual,” said Daniele Michilli, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research. “Not only was it very long, lasting about three seconds, but there were periodic spikes that were remarkably precise, sending out every split second — boom, boom, boom — like a heartbeat. This is the first time that 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 of the signal have dubbed it FRB 20191221A. It is currently the longest-lasting FRB with the clearest periodic pattern discovered to date.
The first FRB was discovered in 2007 and since then hundreds of similar radio bursts have been spotted in space.
The Canadian Hydrogen Intensity Mapping Experiment, or CHIME for short, is an interferometric radio telescope that continuously monitors the sky and is sensitive to fast radio bursts.
Most FRBs are one-time and last a few milliseconds before ending. However, a signal was recently discovered that repeated every 16 days, although the signal was random rather than periodic.
But in December 2019, CHIME discovered the periodic, heartbeat-like signal. At this point, Michilli was scanning the incoming data. “There aren’t many things in the universe that emit strictly periodic signals,” Michilli said.
The source of the new FRB remains a mystery, but scientists believe it could be from a radio pulsar or magnetar, which are neutron stars. These are dense, rapidly spinning, collapsed cores of giant stars.
“CHIME has now discovered many FRBs with different properties,” said Michilli. “We’ve seen some living in very turbulent clouds, while others look like they’re in a clean environment. Based on the properties of this new signal, we can say that around this source there must be a plasma cloud that is extremely turbulent.”
They hope to catch more bursts from FRB 20191221A. The evidence could help them study the universe and neutron stars.
“This discovery raises the question of what could be causing this extreme signal that we have never seen before and how we can use this signal to study the Universe,” Michilli said. “Future telescopes promise to discover thousands of FRBs every month, and at this point we could find many more of these periodic signals.”
More periodic signals from this source could be used as an astrophysical clock. “For example, 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 said.