Astronomers have just spotted the brightest fast radio burst (FRB) ever seen—and for the first time, they know exactly where it came from.
This discovery, made by an international team including researchers from the University of Toronto, could help solve one of astronomy’s biggest mysteries.
FRBs are brief, powerful flashes of radio waves from deep space.
They last only milliseconds to a few seconds, but in that short time, they can outshine every other radio source in their galaxy. Scientists believe they are caused by extreme cosmic events, but no one is sure exactly what triggers them.
The new burst, officially called FRB 20250316A, has been nicknamed RBFLOAT—short for “radio brightest flash of all time.”
It was detected on March 16, 2025, using the Canadian Hydrogen-Intensity Mapping Experiment (CHIME), a giant radio telescope in British Columbia that has recorded thousands of FRBs since 2018.
What made this event so special is that smaller CHIME “outrigger” telescopes—built in British Columbia, Northern California, and West Virginia—were online at the same time.
Together, they used a technique called very long baseline interferometry (VLBI), which combines signals from telescopes spread across large distances. This allowed astronomers to pinpoint the burst’s location with incredible accuracy.
In fact, they could narrow it down to a patch of sky only 45 light-years across. To put that in perspective, that’s like being able to spot a guitar pick from 1,000 kilometers away.
RBFLOAT came from the outskirts of a galaxy called NGC 4141, about 130 million light-years away in the constellation Ursa Major. In cosmic terms, that’s practically next door.
The burst itself lasted just one-fifth of a second. Luckily, it happened only hours before one of the outrigger telescopes lost power. If it had gone off later, the team might never have been able to localize it so precisely.
Because the burst was so bright and so close, astronomers rushed to follow up. Using the James Webb Space Telescope (JWST), they captured a faint infrared signal from the same spot. This could be a nearby red giant star—or possibly a fading “light echo” from the FRB itself. Either way, it marks the first time individual stars have been resolved in the environment of an FRB.
That detail could be key to understanding what causes these bursts. Some theories suggest they come from magnetars—highly magnetic neutron stars—while others point to explosive cosmic events.
Interestingly, despite its brightness, RBFLOAT hasn’t repeated. Most well-studied FRBs do repeat, sometimes many times. The fact that this one hasn’t been seen again challenges the idea that all FRBs are repeaters. Instead, it suggests at least some may come from one-time explosive events.
Two new studies in The Astrophysical Journal Letters describe the discovery: one focused on the radio detection and pinpointing of the burst, and the other on the JWST follow-up.
Together, they open a new chapter in FRB science—using these mysterious flashes not just as puzzles to solve, but as tools to explore the universe itself.
