The brightest cosmic radio flash ever seen has been traced to a nearby galaxy, offering the clearest view yet of one of astronomy’s biggest mysteries.
An international team of astronomers, including researchers from the University of Toronto, has detected the most luminous Fast Radio Burst (FRB) ever recorded. By combining data from a network of radio telescopes, the scientists successfully pinpointed the burst’s exact location in a nearby galaxy. FRBs are among the most puzzling phenomena in astrophysics, but being able to precisely trace their origins marks a major step forward in understanding where and how these cosmic flashes are produced.
Fast Radio Bursts are incredibly energetic, short-lived pulses of radio waves that originate from distant regions across the universe. Their exact causes remain unknown, though they are believed to be linked to extreme astrophysical processes. Since 2018, the Canadian Hydrogen-Intensity Mapping Experiment (CHIME) has discovered thousands of FRBs, yet determining their exact positions in the sky has long been a challenge.
Pinpointing RBFLOAT, the brightest FRB ever observed
The newly identified signal, designated FRB 20250316A and nicknamed RBFLOAT (“Radio Brightest Flash Of All Time”), was localized with remarkable precision using the CHIME/FRB Outrigger array. These smaller telescopes, located in British Columbia, Northern California, and West Virginia, work together using a method called Very Long Baseline Interferometry (VLBI), which allows astronomers to identify the source of an FRB with exceptional 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.”
Despite their immense power, FRBs last for only a few milliseconds or seconds, briefly outshining every other radio source in their galaxy. RBFLOAT, which was detected on March 16, 2025, lasted for just 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.”
Tracing the source to a nearby galaxy
RBFLOAT’s extraordinary brightness was partly due to its proximity, originating from the outer region of a galaxy known as NGC 4141, located approximately 130 million light-years away in the constellation Ursa Major. The researchers were able to pinpoint the source to a compact region only 45 light-years across—smaller than a typical star cluster—achieving an unprecedented level of precision. To put this resolution in perspective, it is equivalent to identifying the location of a guitar pick from 1,000 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.
“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.
Challenging assumptions about FRBs
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 on August 25 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.
References:
“FRB 20250316A: A Brilliant and Nearby One-off Fast Radio Burst Localized to 13 pc Precision” by Thomas C. Abbott, Daniel Amouyal, Bridget C. Andersen, Shion E. Andrew, Kevin Bandura, Mohit Bhardwaj, Kalyani Bhopi, Yash Bhusare, Charanjot Brar, Alice Cai, Tomas Cassanelli, Shami Chatterjee, Jean-François Cliche, Amanda M. Cook, Alice P. Curtin, Evan Davies-Velie, Matt Dobbs, Fengqiu Adam Dong, Yuxin Dong, Gwendolyn Eadie, Tarraneh Eftekhari, Wen-fai Fong, Emmanuel Fonseca, B. M. Gaensler, Nina Gusinskaia, Jason W. T. Hessels, Danté M. Hewitt, Jeff Huang, Naman Jain, Ronniy. C. Joseph, Lordrick Kahinga, Victoria M. Kaspi, Afrasiyab (Afrokk) Khan, Bikash Kharel, Adam E. Lanman, Magnus L’Argent, Mattias Lazda, Calvin Leung, Robert Main, Lluis Mas-Ribas, Kiyoshi W. Masui, Kyle McGregor, Ryan Mckinven, Juan Mena-Parra, Daniele Michilli, Nicole Mulyk, Mason Ng, Kenzie Nimmo, Ayush Pandhi, Swarali Shivraj Patil, Aaron B. Pearlman, Ue-Li Pen, Ziggy Pleunis, J. Xavier Prochaska, Masoud Rafiei-Ravandi, Scott M. Ransom, Gurman Sachdeva, Mawson W. Sammons, Ketan R. Sand, Paul Scholz, Vishwangi Shah, Kaitlyn Shin, Seth R. Siegel, Sunil Simha, Kendrick Smith, Ingrid Stairs, David C. Stenning, Haochen Wang, Thomas Boles, Ismaël Cognard, Tammo Jan Dijkema, Alexei V. Filippenko, Marcin P. Gawroński, Wolfgang Herrmann, Charles D. Kilpatrick, Franz Kirsten, Shawn Knabel, Omar S. Ould-Boukattine, Hadrien Paugnat, Weronika Puchalska, William Sheu, Aswin Suresh, Aaron Tohuvavohu, Tommaso Treu and WeiKang Zheng, 21 August 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/adf62f
“James Webb Space Telescope Observations of the Nearby and Precisely Localized FRB 20250316A: A Potential Near-IR Counterpart and Implications for the Progenitors of Fast Radio Bursts” by Peter K. Blanchard, Edo Berger, Shion E. Andrew, Aswin Suresh, Kohki Uno, Charles D. Kilpatrick, Brian D. Metzger, Harsh Kumar, Navin Sridhar, Amanda M. Cook, Yuxin Dong, Tarraneh Eftekhari, Wen-fai Fong, Walter W. Golay, Daichi Hiramatsu, Ronniy C. Joseph, Victoria M. Kaspi, Mattias Lazda, Calvin Leung, Kiyoshi W. Masui, Juan Mena-Parra, Kenzie Nimmo, Aaron B. Pearlman, Vishwangi Shah, Kaitlyn Shin and Sunil Simha, 21 August 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/adf29f
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