Fast radio bursts (FRBs) are some of the universe’s most mysterious signals — immense flashes of radio waves that last only milliseconds but can outshine every other radio source in their galaxy.
These dazzling flares are so powerful that they can be detected from billions of light-years away.
Now, scientists have caught one of the brightest and closest FRBs ever observed, offering the clearest glimpse yet into the origins of these cosmic enigmas.
An international team, including MIT physicists, detected the flash just 130 million light-years from Earth, in the constellation Ursa Major. The burst was so extraordinarily bright that researchers dubbed it RBFLOAT — “radio brightest flash of all time.”
“Cosmically speaking, this fast radio burst is just in our neighborhood,” says Kiyoshi Masui, associate professor of physics at MIT’s Kavli Institute for Astrophysics and Space Research. “This means we get this chance to study a pretty normal FRB in exquisite detail.”
Pinpointing cosmic fireworks
The groundbreaking detection was made possible by The Canadian Hydrogen Intensity Mapping Experiment (CHIME), a massive radio telescope array in British Columbia, now equipped with a major upgrade.
The addition of CHIME Outriggers — three smaller telescopes spread across North America — has transformed the system into a continent-sized detector capable of pinpointing FRBs with unprecedented accuracy.
“Imagine we are in New York and there’s a firefly in Florida that is bright for a thousandth of a second, which is usually how quick FRBs are,” explains MIT graduate student Shion Andrew. “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.”
On March 16, 2025, CHIME detected an ultrabright flash that initially puzzled astronomers, who wondered if it might be terrestrial interference. But the Outriggers quickly traced the signal to NGC4141, a spiral galaxy in Ursa Major. The burst originated on the edge of a star-forming region — one of the closest and brightest FRBs ever identified.
Hints of older magnetars
The FRB’s position at the outskirts of a star-forming region may provide a clue to its source. Scientists suspect FRBs originate from magnetars — young neutron stars with intense magnetic fields. Typically, magnetars sit at the center of star-forming hubs. This one’s location, slightly offset, suggests it could be older than usual.
“These are mostly hints,” Masui says. “But the precise localization of this burst is letting us dive into the details of how old an FRB source could be. If it were right in the middle, it would only be thousands of years old — very young for a star. This one, being on the edge, may have had a little more time to bake.”
Follow-up analysis revealed that this FRB is a one-off, not a repeater, at least within the six years of CHIME’s data. The distinction matters: while most FRBs are singular events, a small fraction repeat — and an even smaller number do so in patterns, like cosmic heartbeats.
“Right now we’re in the middle of this story of whether repeating and nonrepeating FRBs are different,” Masui says. “These observations are putting together bits and pieces of the puzzle.”
Andrew adds: “There’s evidence to suggest that not all FRB progenitors are the same. We’re on track to localize hundreds of FRBs every year. The hope is that a larger sample of FRBs localized to their host environments can help reveal the full diversity of these populations.”