An international team of scientists, including Northwestern University astrophysicists, has spotted one of the brightest fast radio bursts (FRBs) ever recorded - and pinpointed its location with unprecedented precision.
The millisecond-long blast - nicknamed RBFLOAT (short for "radio-brightest flash of all time" and, yes, a nod to "root beer float") - was discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and its newly completed "Outrigger" array. By combining observations from sites in British Columbia, West Virginia and California, scientists traced the burst to a single spiral arm of a galaxy 130 million light-years away - accurate within just 42 light-years.
Because they occur so far away and vanish within the blink of an eye, FRBs are notoriously difficult to study. If scientists can pinpoint an FRB's exact location, however, they can explore its environment, including characteristics of its home galaxy, distance from Earth and potentially even its cause. Eventually, this information could help shed light on the nature and origins of these mysterious, fleeting bursts.
The study will be published on Thursday (Aug. 21) in The Astrophysical Journal Letters. It marks the first time the full Outrigger array was used to localize an FRB.
"It is remarkable that only a couple of months after the full Outrigger array went online, we discovered an extremely bright FRB in a galaxy in our own cosmic neighborhood," said Northwestern's Wen-fai Fong, a senior author on the study. "This bodes very well for the future. An increase in event rates always provides the opportunity for discovering more rare events. The CHIME/FRB collaboration worked for many years toward this technical achievement, and the universe rewarded us with an absolute gift."
"This result marks a turning point," said corresponding author Amanda Cook, a postdoctoral researcher at McGill University. "Instead of just detecting these mysterious flashes, we can now see exactly where they are coming from. It opens the door for discovering whether they are caused by dying stars, exotic magnetic objects or something we haven't even thought of yet."
An expert on cosmic explosions, Fong is an associate professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences. She also is a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and the NSF-Simons AI Institute for the Sky (SkAI Institute).
Four days of solar energy packed into a single blink
Flaring up and disappearing within milliseconds, FRBs are brief, powerful radio blasts that generate more energy in one quick burst than our sun emits in an entire year. While most pass unnoticed, every once in a while, an FRB is bright enough to detect. FRB20250316A, or RBFLOAT, was one of these rare events. Detected in March 2025, RBFLOAT released as much energy in a few milliseconds as the sun produces in four days.
"It was so bright that our pipeline initially flagged it as radio frequency interference, signals often caused by cell phones or airplanes that are much closer to home," Fong said. "It took some sleuthing by members of our collaboration to uncover that it was a real astrophysical signal."
And while many FRBs repeat - pulsing multiple times across several months - RBFLOAT emitted all its energy in just one burst. Even in the hundreds of hours after it was first observed, astronomers did not detect repeat bursts from the source. That means astrophysicists couldn't wait for another flare to gather more data. Instead, they only had one shot at pinpointing its location.
"RBFLOAT was the first non-repeating source localized to such precision," said Northwestern's Sunil Simha, a postdoctoral scholar at CIERA and study co-author. "These are much harder to locate. Thus, even detecting RBFLOAT is proof of concept that CHIME is indeed capable of detecting such events and building a statistically interesting sample of FRBs."
FRB forensics hint at a magnetar
To investigate RBFLOAT's origin, the scientists relied on CHIME, a large radio telescope in British Columbia and the world's most prolific FRB hunter. Smaller versions of CHIME, the Outriggers enable astronomers to triangulate signals to precisely confine the specific locations of FRBs on the sky.
With this array of vantage points, the team traced the burst to the Big Dipper constellation in the outskirts of a galaxy about 130 million light-years away from Earth. The team precisely pinpointed it to a region just 45 light-years across, which is smaller than an average star cluster.
Follow-up observations from the 6.5-meter MMT telescope in Arizona and the Keck Cosmic Web Imager on the 10-meter Keck II Telescope in Hawai'i provided the most detailed view yet of a non-repeating FRB's surroundings. Simha analyzed the optical data obtained from Keck, and Northwestern graduate student Yuxin "Vic" Dong used the MMT to obtain deep optical images of the FRB's host galaxy.
Their investigations revealed the burst occurred along a spiral arm of the galaxy, which is dotted with many star-forming regions. The RBFLOAT occurred near, but not inside, one of these star-forming regions. Although astrophysicists still don't know exactly what causes FRBs, this evidence bolsters one leading hypothesis. At least some appear to come from magnetars, ultra-magnetized neutron stars born from the deaths of massive stars. Star-forming regions often host young magnetars, which are energetic enough to produce quick, powerful bursts.
"We found the FRB lies at the outskirts of a star-forming region that hosts massive stars," Simha said. "For the first time, we could even estimate how deeply it's embedded in surrounding gas, and it's relatively shallow."
Keck's rich dataset and FRB's precise location enabled the team to perform first-of-its-kind analysis of the galaxy's properties at the FRB's location. These uncovered characteristics include the density of the galaxy's gas, star-formation rate and presence of elements heavier than hydrogen and helium.
"The FRB lies on a spiral arm of its host galaxy," added Dong, who is the principal investigator of the MMT program. "Spiral arms are typically sites of ongoing star formation, which supports the idea that it came from a magnetar. Using our extremely sensitive MMT image, we were able to zoom in further and found that the FRB is actually outside the nearest star-forming clump. This location is intriguing because we would expect it to be located within the clump, where star formation is happening. This could suggest that the progenitor magnetar was kicked from its birth site or that it was born right at the FRB site and away from the clump's center."
The start of something spectacular
With the CHIME Outriggers now fully running, astronomers expect to pin down hundreds more FRBs each year - bringing them closer than ever to solving the mystery of what causes these spectacular flashes. The localization power of the Outriggers, combined with CHIME's wide field of view, marks a turning point for the FRB search.
"For years, we've known FRBs occur all over the sky, but pinning them down has been painstakingly slow," Dong said. "Now, we can routinely tie them to specific galaxies, even down to neighborhoods within those galaxies."
"The entire FRB community has only published about 100 well-localized events in the past eight years," Simha said. "Now, we expect more than 200 precise detections per year from CHIME alone. RBFLOAT was a spectacular source to begin building such a sample."
"Thanks to the CHIME Outriggers, we're now entering a new era of FRB science," said study co-author Tarraneh Eftekhari, who is CIERA's assistant director. "With hundreds of precisely localized events expected in the next few years, we can start to understand the full breadth of environments from which these mysterious signals emanate, bringing us one step closer to unlocking their secrets. RBFLOAT is just the beginning."
The study, "FRB 20250316A: A Brilliant and Nearby One-Off Fast Radio Burst Localized to 13 parsec Precision," was supported by the National Science Foundation, the David and Lucile Packard Foundation, the Alfred P. Sloan Foundation, the Research Corporation of Science Advancement, the Gordon & Betty Moore Foundation, the Canadian Institute for Advanced Research, the Canadian Natural Sciences and Engineering Council of Canada, the Canada Foundation for Innovation and the Trottier Space Institute at McGill. The CHIME collaboration includes astrophysicists from Northwestern, McGill University, the Massachusetts Institute of Technology, University of Toronto, University of British Columbia and several other institutions.
