Astronomers have discovered what may be the brightest flash of radio waves ever seen and have tracked this fast radio burst (FRB) back to its source. This feat could revolutionize theories surrounding these mysterious and rapid blasts of radiation that, in mere milliseconds, can emit as much energy as the sun does in its entire lifetime.
First spotted in 2007, FRBs have been difficult for astronomers to explain. This is because they last such a brief amount of time and only a small sample of them repeat, making follow-up investigations difficult. Though many explanations have been posited for FRBs, the leading culprits are extreme dead stars or “neutron stars” with magnetic fields so powerful they warrant a categorization of their own and are thus dubbed “magnetars.”
The new FRB has been officially designated FRB 20250316A and has been given the nickname “RBFLOAT,” which stands for “Radio Brightest FLash Of All Time.” This unusually bright FRB was first spotted in March 2025 by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which has been dubbed an “FRB discovery machine” thanks to its immense impact in spotting new FRBs.
This is the first time the CHIME/FRB radio telescope has been used on its own to track an FRB back to its source. In this case, that source is a region just 45 light-years across – smaller than the average star cluster – in the spiral arm at the edge of NGC 4141, a galaxy about 130 million light-years away. To put that feat into context, the team behind the research compares it to spotting a quarter from a distance of 62 miles away.
“This result marks a turning point: instead of just detecting these mysterious flashes, we can now see exactly where they’re coming from. It opens the door to discovering whether they’re caused by dying stars, exotic magnetic objects, or something we haven’t thought of yet,” team leader and McGill University researcher Amanda Cook said in a statement.
CHIME now has the spatial resolution to track back an FRB in this way, thanks to its newly constructed “outrigger” telescopes located throughout North America from British Columbia to California.
“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,” Cook said. “The precision of this localization, tens of milliarcseconds, is like spotting a quarter from 100 kilometres (62 miles) away. That level of detail is what let us identify the host galaxy, NGC 4141, and match the burst with a faint infrared signal captured by the James Webb Space Telescope (JWST).”
This was the first time that astronomers were able to trace an FRB back to its source rapidly enough to follow up with the powerful infrared vision of the JWST.
“We were rewarded with an exciting result – we see a faint source of infrared light very close to where the radio burst occurred,” team member Peter Blanchard, research associate in the Harvard College Observatory at the Center for Astrophysics | Harvard & Smithsonian (CfA), said in a statement. “This could be the first object linked to an FRB that anyone has found in another galaxy.”
The infrared object located by the RBFLOAT source has been dubbed NIR-1, and it is believed to be a red giant star or a middle-aged massive star. Red giants represent one of the final stages of stars with masses similar to that of the sun, after they have exhausted the hydrogen fuel in their cores and that core collapses as the star’s outer shell “puffs out” to as much as 100 times its original diameter.
But whatever NIR-1 is, it is unlikely to be the cause of RBFLOAT. Red giants and massive stars aren’t generally associated with phenomena that could trigger such an outburst.
What Blanchard and colleagues theorize is that NIR-1 has a more extreme companion in the form of a neutron star, a dead stellar core that forms when stars around 10 times more massive than the sun die. The immense gravity of this neutron star could be stripping material away from NIR-1, with this process being integral to the launch of this bright FRB.
“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.”
If the infrared source begins to fade over time, it could indicate that it is actually reflected light caused by flaring of whatever object launched RBFLOAT, possibly a magnetar.
The brightness of RBFLOAT and its relative proximity to Earth (many FRBs have been traced to sources billions of light-years away), combined with the fact that the JWST was able to capture detailed images of the region from which it originated, means that it could prove integral to investigating these puzzling blasts of radiation.
“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,” Berger concluded. “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.”
Two papers regarding the discovery of RBFLOAT have been published in The Astrophysical Journal Letters.