For a fraction of a second — roughly one-fifth of a second, to be precise — something in a galaxy 130 million light-years from Earth released a burst of radio energy so powerful that it briefly **outshone every other radio source in its host galaxy combined**.
It happened on March 16, 2025. Astronomers didn't fully understand what they had captured until a year later, when the detailed analysis was published in the *Astrophysical Journal Letters* in March 2026. And the results have electrified the field.
The burst has been given the formal designation **FRB 20250316A** and the informal name **RBFLOAT** — for *Radio Brightest FLash Of All Time*. It is the most luminous fast radio burst ever detected. And for the first time, researchers have pinpointed the origin of such a burst with extraordinary precision — to a region just **45 light-years across** in a galaxy in the constellation Ursa Major.
**What a Fast Radio Burst Is**
Fast radio bursts — FRBs — are among the most bizarre phenomena in the observable universe. They are immense flashes of radio emission lasting milliseconds. They come from deep space. They carry enormous energy — a single burst can release as much energy as the Sun emits over three days, compressed into a few thousandths of a second. And their cause, despite over 4,000 detections since the first confirmed discovery in 2007, remains one of astrophysics' deepest unsolved mysteries.
Leading theories point to **magnetars** — exotic, ultra-dense neutron stars with colossal magnetic fields — as one possible source. But not all FRBs fit the magnetar model neatly, and RBFLOAT adds a new complication: it has not repeated. Not once.
"At the level of our detection sensitivity, this FRB has not repeated," says **Kiyoshi Masui**, associate professor of physics at MIT and affiliate of MIT's Kavli Institute for Astrophysics and Space Research. "That challenges some of our existing theories about what causes these things."
**The Telescope That Changed Everything**
The detection was made by **CHIME** — the Canadian Hydrogen Intensity Mapping Experiment, a large array of half-pipe-shaped antennae located in British Columbia, Canada. CHIME has been detecting FRBs since 2018, accumulating a catalogue of roughly 4,000 events. But until recently, CHIME could not tell you *exactly where* an FRB came from.
That changed with the completion of **CHIME Outriggers** — three miniature versions of CHIME placed in geographically separate locations across North America: one in British Columbia, one in Northern California, and one in West Virginia. Together, the four stations form a continent-spanning interferometer — a single telescope, effectively, with a baseline of thousands of kilometres.
The physics of interferometry means that the wider your telescope baseline, the more precisely you can pinpoint where a signal came from. CHIME plus its three Outriggers created a system capable of localising fast radio bursts to an area the size of a single star-forming region within a distant galaxy.
RBFLOAT was the first major FRB detected with the completed Outrigger array. And the precision was everything scientists had hoped for.
**A Firefly in Florida, Seen from New York**
To illustrate what the localisation achievement means, MIT Kavli graduate student **Shion Andrew** offered a vivid analogy:
*"Imagine we are in New York and there's a firefly in Florida that is bright for a thousandth of a second. Localizing an FRB to a specific part of its host galaxy is analogous to figuring out not just what tree the firefly came from, but which branch it's sitting on."*
The branch, in RBFLOAT's case, is a region on the **outer edge** of galaxy **NGC 4141** — a spiral galaxy in Ursa Major — just outside one of its star-forming areas. The burst arose not from the galaxy's centre, not from a dense star cluster, but from the galaxy's quieter periphery. That location is now being studied for clues about what kind of environment brews up such events.
"As we're getting these much more precise looks at FRBs, we're better able to see the diversity of environments they're coming from," says MIT physics postdoc **Adam Lanman**.
**The James Webb Surprise**
Following the radio detection, astronomers trained the **James Webb Space Telescope** on the same location. JWST found a faint **infrared signal** at the precise position of the radio burst — a signal that scientists are still working to explain.
Whether the infrared emission is related to the FRB mechanism, to the stellar population in that region, or to something else entirely is not yet clear. But the fact that the CHIME localisation was precise enough to point JWST at the right spot — among hundreds of billions of stars in a galaxy 130 million light-years away — is itself a demonstration of what the new telescope system can do.
**Why This Matters**
Fast radio bursts are more than an astronomical curiosity. Because they travel through the intergalactic medium — the thin plasma that fills the space between galaxies — the way their signal disperses as they travel encodes information about how much matter exists between us and their source. FRBs have already been used to measure the density of intergalactic matter, contributing to cosmological measurements that are otherwise extremely difficult to make.
The brighter and closer the FRB, the more information it carries. RBFLOAT — 130 million light-years away, far closer than most FRBs, and far brighter — offers an exceptional data quality that may help answer not just where FRBs come from, but how matter is distributed across the universe between galaxies.
"Cosmically speaking, this fast radio burst is just in our neighborhood," says Masui. "This means we get this chance to study a pretty normal FRB in exquisite detail."
The universe has been sending these extraordinary flashes across the cosmos for billions of years. We are finally developing the instruments to not just detect them, but to find them — and follow them home. ✨📡
*Sources: Astrophysical Journal Letters (March 2026) · MIT Kavli Institute for Astrophysics and Space Research · CHIME/FRB Collaboration · MIT Physics (physics.mit.edu) · University of Toronto · McGill University · Smithsonian Magazine · ScienceDaily (March 15, 2026)*
