An international team has identified the brightest fast radio burst ever detected by CHIME, tracing it to the galaxy NGC 4141. Named FRB 20250316A or RBFLOAT, the burst occurred on March 16, 2025, and lasted about one-fifth of a second. Follow-up observations with the James Webb Space Telescope revealed a faint infrared signal at the location.
Astronomers using the CHIME/FRB Outrigger array—telescopes in British Columbia, Northern California, and West Virginia—localized FRB 20250316A with high precision on March 16, 2025. This burst, nicknamed RBFLOAT for 'Radio Brightest Flash Of All Time,' originated in the outer region of NGC 4141, a galaxy 130 million light-years away in Ursa Major. The localization narrowed the source to a 45 light-year region, achieved via Very Long Baseline Interferometry (VLBI). The event briefly outshone all other radio sources in its galaxy but showed no repeats despite six years of CHIME monitoring covering hundreds of hours in the area. A power outage shortly after detection nearly prevented precise positioning, as noted by University of Toronto doctoral student Mattias Lazda: “We were ultimately extremely lucky that we were able to pinpoint the precise sky position of this rare event... Had the event happened any later that day, we would’ve completely missed our chance.” Follow-up with the James Webb Space Telescope (JWST) detected a faint infrared signal at the site, possibly from a red giant star or a light echo. Harvard postdoctoral fellow Peter Blanchard stated: “The high resolution of JWST allows us to resolve individual stars around an FRB for the first time.” Kiyoshi Masui, associate professor of physics, called it “just in our neighborhood,” enabling detailed study. McGill researcher Amanda Cook highlighted its non-repeating nature: “This burst doesn’t seem to repeat, which makes it different from most well-studied FRBs... That challenges a major idea in the field.” Two papers detailing the detection and JWST observations appear in the Astrophysical Journal Letters.