Origin of Mysterious Radio Signal Possibly Discovered

Cambridge, MA - Astronomers have discovered what may be the source of a powerful burst of radio waves coming from another galaxy. Using precise radio and infrared data, the scientists made the deepest search yet for a source of these mysterious, fleeting signals – and addressed a major unsolved problem in astrophysics in the process.

The research team, led by Peter Blanchard, research associate in the Harvard College Observatory at the Center for Astrophysics | Harvard & Smithsonian (CfA), may have found, for the first time, an object that produced a fast radio burst, or FRB, in another galaxy.

These FRBs are powerful bursts of radio wave emission that last only a few milliseconds, or a tiny fraction of a second. Since astronomers first discovered FRBs in 2007, they have determined the waves originate from outside our galaxy, including some that are billions of light-years from Earth.

However, understanding and explaining these extraordinary phenomena has been a daunting challenge. One leading idea is that FRBs are connected to magnetars: neutron star remnants of supernova explosions with powerful magnetic fields. Many other explanations, however, are possible because astronomers have not found reliable signals from the sources that produce FRBs in light at other wavelengths including visible and infrared light, which falls just outside the visible spectrum.

Blanchard and his team used a discovery of an FRB in a nearby galaxy made with the CHIME Outriggers array, a radio telescope in Canada, which was recently upgraded to enable FRB detections with precise positions. The researchers then turned to NASA’s James Webb Space Telescope (JWST) to look for an infrared signal from the same location.

"This was a unique opportunity to quickly turn JWST’s powerful infrared eye on the location of an FRB for the first time," said Blanchard. "And we were rewarded with an exciting result – we see a faint source of infrared light very close to where the radio burst occurred. This could be the first object linked to an FRB that anyone has found in another galaxy."

The infrared data revealed an object, dubbed NIR-1, that is likely a red giant star or possibly a middle-aged massive star. A red giant is a Sun-like star near the end of its life that has expanded and brightened, while the other possibility is a star much more massive than the Sun.

Although these stars are unlikely to directly produce FRBs, the scientists say, they may have an unseen companion, such as a neutron star, pulling material away from the red giant or massive star. This process of transferring mass may have triggered the FRB.

The new fast radio burst, named FRB 20250316A, was discovered on March 16 2025, in the galaxy NGC 4141 about 130 million light-years away from Earth. It is an exceptional target for follow-up studies because it is the nearest FRB yet found with the upgraded CHIME Outrigger array , enabling one of the most accurate radio positions ever obtained for an FRB.

"With the CHIME Outriggers, we are finally catching these fleeting cosmic signals in the act—narrowing down their locations not only to individual galaxies, but even to specific stellar environments," said co-author Amanda Cook, a postdoctoral researcher from McGill University and lead of a companion paper on the CHIME discovery of this FRB.

The advantages of its relatively close proximity and precise location, combined with the sharp JWST images, allowed the clearest view of individual stars ever seen around an FRB’s location.

"Dozens of different ideas have been proposed to explain FRBs, but until now we haven’t had the data to test most of them," said co-author Edo Berger, CfA scientist and professor of astronomy at Harvard. "Being able to isolate individual stars around an FRB is a huge gain over previous searches, and it begins to tell us what sort of stellar systems could produce these powerful bursts."

The red giant or massive star could, however, be unrelated to the FRB, which motivated the team to study its larger environment for any additional clues. They found the FRB is located near a small cluster of young massive stars. Based on this location, they suggested that a massive star in the cluster may have already collapsed to form a magnetar, which produced the FRB. A magnetar would be much too faint to be directly seen in the JWST data.

The team considered several other possible explanations for the FRB, including an object in a dense cluster of old stars, or a massive giant star. These would be brighter than the faint star they observed, so these explanations were ruled out.

"Whether or not the association with the star is real, we’ve learned a lot about the burst’s origin," said Blanchard. "If a double star system isn’t the answer, our work hints that an isolated magnetar caused the FRB."

Another possible explanation for the infrared signal is that it is reflected light caused by a flare from the object that caused the radio burst, such as from a magnetar. If so, the infrared light is likely to fade over time. Their team will propose more JWST observations to search for such a change.

"We have taken the first step on a new path to solving the mystery of FRBs using the sharp imaging of JWST to zoom in on the precise locations from which FRBs are emanating ," said Berger. "We can’t predict when and where the next FRB will come from, so we have to be ready to quickly deploy JWST when the time comes."

A paper describing these results is being published today in The Astrophysical Journal Letters. Full details about the CHIME discovery are being published today in the same issue of The Astrophysical Journal Letters and are described in a press release from McGill University.

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