The brightest cosmic radio flash ever recorded has been traced to a nearby galaxy, providing unprecedented insights into one of astronomy”s most intriguing enigmas. An international team of astronomers, including experts from the University of Toronto, has successfully identified the most luminous Fast Radio Burst (FRB) to date. By integrating data from a network of radio telescopes, the researchers accurately located the burst”s origin in a nearby galaxy.
FRBs represent some of the most enigmatic phenomena in astrophysics. Being able to trace their origins with such precision marks a significant advancement in understanding the mechanisms behind these cosmic signals. Fast Radio Bursts are extremely powerful, fleeting pulses of radio waves emitted from distant parts of the universe, though their exact origins remain largely unknown. They are thought to be associated with extreme astrophysical processes.
Since its inception in 2018, the Canadian Hydrogen-Intensity Mapping Experiment (CHIME) has discovered thousands of FRBs. However, pinpointing their exact locations in the sky has proven to be a daunting task. The newly identified signal, labeled FRB 20250316A and nicknamed RBFLOAT (which stands for “Radio Brightest Flash Of All Time”), was precisely localized using the CHIME/FRB Outrigger array. This array of smaller telescopes, situated across British Columbia, Northern California, and West Virginia, employs a technique known as Very Long Baseline Interferometry (VLBI) to achieve exceptional accuracy in identifying sources of FRBs.
“We were ultimately extremely lucky that we were able to pinpoint the precise sky position of this rare event,” stated Mattias Lazda, a doctoral student at the University of Toronto and co-author of the research. “A few hours after we detected it, we experienced a power outage at one of our telescope sites that played a critical role in telling us where the burst came from. Had the event happened any later that day, we would”ve completely missed our chance.”
Despite their extraordinary energy, FRBs are short-lived, persisting only for milliseconds or seconds, and can briefly outshine all other radio sources in their galaxy. RBFLOAT, detected on March 16, 2025, lasted merely a fifth of a second. “Cosmically speaking, this fast radio burst is just in our neighborhood,” remarked Kiyoshi Masui, an associate professor of physics affiliated with MIT”s Kavli Institute for Astrophysics and Space Research and a graduate of the University of Toronto. “This means we get this chance to study a pretty normal FRB in exquisite detail.”
RBFLOAT”s remarkable brightness is partly attributed to its close proximity, originating from the outer regions of a galaxy known as NGC 4141, located roughly 130 million light-years away in the constellation Ursa Major. The research team was able to narrow the source down to a compact region only 45 light-years across, achieving an unprecedented level of precision. This resolution is comparable to identifying the location of a guitar pick from a distance of 1,000 kilometers.
“The discovery was very exciting because we had our brightest ever event right after all three outriggers were online,” said Amanda Cook, a Banting Postdoctoral Researcher at McGill University and a University of Toronto alum who led the paper discussing RBFLOAT. “Immediately, even though it was a Sunday afternoon, a bunch of us piled into a Zoom room and started working on the research, hoping to get follow-up observations on the source as quickly as possible.”
The detailed observations provided by the CHIME/FRB Outrigger array enabled the team to conduct follow-up studies with the James Webb Space Telescope (JWST), capturing a faint infrared signal that corresponded to the location of RBFLOAT. This finding surprised the researchers, who are now contemplating whether the signal could be from a red giant star or a fading light echo from the burst itself. “The high resolution of JWST allows us to resolve individual stars around an FRB for the first time,” stated Peter Blanchard, a postdoctoral fellow at Harvard and lead author of the companion paper detailing the JWST observation. “This opens the door to identifying the kinds of stellar environments that could give rise to such powerful bursts, especially when rare FRBs are captured with this level of detail.”
Despite being the brightest FRB ever detected by CHIME, astronomers have not observed any repeating bursts from this source, even after reviewing hundreds of hours of observations over more than six years. “This burst doesn”t seem to repeat, which makes it different from most well-studied FRBs,” remarked Cook. “That challenges a major idea in the field, that all FRBs repeat, and opens the door to reconsidering more “explosive” origins for at least some of them.”
Two studies detailing these findings were published on August 25 in the Astrophysical Journal Letters: one focuses on the original radio discovery and localization of the burst, while the other discusses JWST”s near-infrared images of the FRB”s origin. Together, they offer new insights into FRBs, presenting them not just as cosmic curiosities but as valuable tools for probing the universe.
