MIT researchers have detected an unusual radio signal from a distant galaxy


Fast radio signals usually last a few milliseconds. Scientists found one that lasted much longer.

Using the CHIME radio telescope, astronomers detected an unusual signal from a distant galaxy. CHIME, with background edited by MIT News

Astronomers from Canada and MIT have detected an intriguing and unusually persistent radio signal from a galaxy several billion light years from Earth.

According to MIT, the signal is what’s known as a fast radio burst, or FRB. These massively strong bursts of radio waves typically last a few milliseconds. What sets this new signal apart is that it lasts up to three seconds. Adding to the mystery, this FRB was punctuated by periodic bursts of radio waves that repeated every 0.2 seconds in a distinct pattern.

The signal, designated FRB 20191221A, is the longest-lasting FRB ever detected. It also has the clearest periodic pattern ever seen in an FRB, according to MIT.

Although this signal can be pinpointed to a certain distant galaxy, its exact source is unknown. Right now, evidence suggests it came from a radio pulsar or magnetar, two types of neutron star, according to the university. They are formed when stars more massive than the Sun explode in supernovae. Their outer layers can blow away, leaving behind a small, incredibly dense core that is constantly collapsing. The force of gravity is so strong that protons and electrons combine to create neutrons, hence the name.

“There aren’t many things in the universe that emit strictly periodic signals,” Daniele Michilli, a postdoctoral fellow at MIT’s Kavli Institute for Astrophysics and Space Exploration, said in a statement. “Examples we know of in our own galaxy are radio pulsars and magnetars, which rotate and produce a beam similar to the emission of a lighthouse. And we think this new signal could be a magnetar or a pulsar on steroids.”

The discovery of this FRB was published in the journal Nature this week. Calvin Leung, Juan Mena-Parra, Kaitlyn Shin and Kiyoshi Masui of MIT co-authored the paper with Michilli.

The signal was detected by Canada’s Hydrogen Intensity Mapping Experiment, or CHIME. This radio telescope, located in British Columbia, continuously scans the sky for radio waves emitted in the early ages of the universe. It is also sensitive to FRBs and has detected hundreds of these signals since 2018.

While still working as a researcher at McGill University in December 2019, Michilli was reading incoming CHIME data when he noticed something strange.

“It was unusual,” he said, according to MIT. “Not only was it very long, about three seconds long, but there were periodic peaks that were incredibly precise, emitting every fraction of a second — boom, boom, boom — like a heartbeat. This is the first time that the signal itself is periodic.”

Michilli told MIT that the intense flares detected in this FRB could come from a neutron star that isn’t normally very bright as it rotates, but for some reason emitted a large burst of flares over a three-second period that CHIME happened to catch.

“CHIME has now detected many FRBs with different properties,” Michilli said. “We have seen some that live inside clouds that are very turbulent, while others appear to be in clean environments. From the properties of this new signal, we can say that there is a plasma cloud around this source that must be extremely turbulent.”

Astronomers now hope to capture more periodic radio signals from this source, according to MIT. If they do, the signals could be used as a way to measure the rate at which the universe is expanding.

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