
Artist’s rendition of CHIME/FRB and its Outriggers localizing FRB 20250316A/ RBFLOAT. Inset: The host galaxy (NGC 4141) as imaged by MMT Observatory (PI: Yuxin (Vic) Dong), illustrating the location of the FRB within a spiral arm of NGC 4141. Image credits: Daniëlle Futselaar/MMT Observatory
An international collaboration of astronomers, including members from the University of Toronto, have detected the brightest Fast Radio Burst (FRB) to date, and using a network of radio telescopes, have been able to pinpoint its location in a nearby galaxy. FRBs remain one of astronomy’s most mysterious phenomena, but precisely determining their location will mean the beginning of a new era where their cosmic origins can be traced.
FRBs are extremely energetic flashes from distant sources from across the universe. They are caused by extreme astrophysical phenomena not yet understood by scientists. The Canadian Hydrogen-Intensity Mapping Experiment, or CHIME, has detected thousands of FRBs since 2018, though precisely locating their origin on the sky has been difficult.
The new FRB signal, called FRB 20250316A and playfully nicknamed RBFLOAT (“Radio Brightest Flash Of All Time”), was very precisely localized using the new CHIME/FRB Outrigger array. These smaller versions of the CHIME instrument located in British Columbia, Northern California and West Virginia allow astronomers to perform Very Long Baseline Interferometry (VLBI), a technique that can pinpoint the location of FRBs with unprecedented accuracy.
“We were ultimately extremely lucky that we were able to pinpoint the precise sky position of this rare event,” said Mattias Lazda, doctoral student at the University of Toronto, and an author on both papers. “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.”
Though FRBs are some of the most powerful radio sources in the universe, they last only a few milliseconds to seconds, momentarily outshining all other radio sources in their galaxy. RBFLOAT, detected on March 16, 2025, lasted only about one fifth of a second.
“Cosmically speaking, this fast radio burst is just in our neighborhood,” says Kiyoshi Masui, associate professor of physics and affiliate of MIT’s Kavli Institute for Astrophysics and Space Research, and a U of T alum. “This means we get this chance to study a pretty normal FRB in exquisite detail.”
RBFLOAT was so bright because the source was relatively nearby in the outskirts of a galaxy called NGC 4141, which is about 130 million light-years away in the constellation Ursa Major. The signal was traced to a region only 45 light-years across – smaller than the average star cluster – representing an unprecedented spatial resolution. It is equivalent to observing a guitar pick from 1000 kilometers away!
“The discovery was very exciting, because we had our brightest ever event right after all three outriggers were online” said Amanda Cook, Banting Postdoctoral Researcher at McGill University and a U of T alum who led the paper describing RBFLOAT. “Immediately, even though it was a Sunday afternoon, a bunch of us piled into a zoom room and started hacking away at the research, hoping to get follow-up observations on source as quickly as possible.”
The level of detail provided by the CHIME/FRB Outrigger array was what allowed the team to follow up with observations from the James Webb Space Telescope (JWST) and capture a faint infrared signal that matched the location of RBFLOAT. This surprised the researchers who are left wondering if the spot is something like a red giant star or a fading light echo from the burst itself.

A colour image of galaxy NGC 4141 composed of two JWST images. The inset shows the area containing the precise location of FRB 20250316A/RBFLOAT and its potential infrared counterpart, NIR-1. Credit: NASA/ESA/CSA/CfA/P. Blanchard et al.; Image processing: CfA/P. Edmonds
“The high resolution of JWST allows us to resolve individual stars around an FRB for the first time. 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.” said Peter Blanchard, a Harvard postdoctoral fellow and lead author of the companion paper describing the JWST observation.
Despite being the brightest ever seen by CHIME, astronomers have not detected repeat bursts from the source, even when looking back over the hundreds of hours of CHIME observations of its position over more than six years.
“This burst doesn’t seem to repeat, which makes it different from most well-studied FRBs,” said 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 describing the phenomenon were published today in The Astrophysical Journal Letters: one is focused on the original radio discovery and localization of the burst, and the other on JWSTs near-infrared images of the location from which the radio burst originated. Together, they provide detail and new possibilities for studying FRBs, not just as cosmic curiosities but as tools to probe the universe.
- “FRB 20250316A: A Brilliant and Nearby One-Off Fast Radio Burst Localized to 13 parsec Precision” by the CHIME/FRB Collaboration which includes astrophysicists from McGill, the Massachusetts Institute of Technology, the University of Toronto, Northwestern University, and many other institutions.
- “James Webb Space Telescope Observations of the Nearby and Precisely-Localized FRB 20250316A” led by Peter Blanchard and Edo Berger of the Center for Astrophysics | Harvard & Smithsonian, and members of the CHIME/FRB Collaboration.
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The Dunlap Institute for Astronomy & Astrophysics in the Faculty of Arts & Science at the University of Toronto is an endowed research institute with over 80 faculty, postdocs, students, and staff, dedicated to innovative technology, groundbreaking research, world-class training, and public engagement.
The research themes of its faculty and Dunlap Fellows span the Universe and include optical, infrared and radio instrumentation, Dark Energy, large-scale structure, the Cosmic Microwave Background, the interstellar medium, galaxy evolution, cosmic magnetism and time-domain science.
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