‘Brightest of all time’: James Webb telescope pinpoints origin of brightest flash of radio light ever detected
For the first time, scientists have used the James Webb Space Telescope (JWST) to study the origins of a bizarre, record-breaking radio signal that flashed past Earth earlier this year.
Tracking the bright radio burst to the edge of a galaxy some 130 million light-years from Earth, the researchers used JWST’s infrared eye to identify a powerful explosion of energy coming from a large, old star that may be the strange signal’s progenitor. The team also zoomed in on specific stars clustered nearby, painting a picture of the radio burst’s original environment with unprecedented clarity.
The findings, described in two papers published Aug. 21 in The Astrophysical Journal Letters, may mark a turning point in the study of fast radio bursts (FRBs), which to date have proved extremely challenging to trace to their original galaxies, let alone to the specific star systems that birthed them.
“The high resolution of JWST allows us to resolve individual stars around an FRB for the first time,” Peter Blanchard, a research scientist at Harvard University and lead author of one of the papers, said in a statement. “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.”
‘Floating’ new possibilities
True to their name, fast radio bursts are incredibly brief pulses of radio energy. They often last just a few milliseconds but emit more power in that time than the sun does in several days.
Since the phenomenon’s discovery in 2007, scientists have detected more than 1,000 FRBs blasting outward from all corners of the sky. However, the pulses’ ultrashort duration makes them difficult to study. Many of the strange signals seem to repeat, but some don’t. There are several theories for what causes FRBs, with the leading contender being magnetars — fast-spinning, highly magnetized husks of dead stars called neutron stars. But this, too, is uncertain.
In March, astronomers at the Canadian Hydrogen Intensity Mapping Experiment (CHIME) — an array of more than 1,000 radio receivers devoted to studying FRBs — spotted the single brightest radio burst ever detected at the facility. Officially named FRB 20250316A, the team dubbed the powerful burst “RBFLOAT,” short for Radio Brightest Flash Of All Time.
Related: Fast radio burst traced to the outskirts of an ancient ‘graveyard’ galaxy — and the cause remains a mystery
The burst’s extreme brightness hinted that the FRB originated relatively close to the Milky Way, according to the researchers — and made it a perfect target for CHIME’s new Outrigger array, a suite of telescopes spanning North America, from California to British Columbia. Studying the powerful FRB from multiple vantage points, the researchers pinned its location to the galaxy NGC 4141, located inside the Big Dipper, and then further narrowed the burst’s origin to a region of space measuring just 45 light-years across. (For comparison, our Milky Way galaxy spans about 100,000 light-years).
“The precision of this localization … is like spotting a quarter from 100 kilometres [62 miles] away,” Amanda Cook, a postdoctoral researcher at McGill University and lead author of the second paper, said in the statement.
Following CHIME’s initial detective work, the team enlisted the help of the mighty JWST, which zoomed in on the narrow region of space where RBFLOAT originated. The telescope not only detected a burst of infrared energy located in the exact spot where the FRB had been detected but also examined individual stars in the surrounding neighborhood to characterize the environment from which the radio burst emanated.
“This could be the first object linked to an FRB that anyone has found in another galaxy,” Blanchard said in another statement.
JWST’s data showed that the infrared object is either a red giant star (a star that has swelled as it nears the end of its life) or a massive, middle-aged star many times larger than the sun. While neither type of star is a viable source of FRBs, it’s plausible that an unseen companion star — such as an energy-spewing neutron star — orbits the infrared object, the team added. If that’s the case, the companion star may be siphoning material off of its larger host, which could have triggered the bright radio burst.
By studying the surrounding environment, which is replete with young-but-massive stars, the team also proposed a second hypothesis: that one of the larger stars in the cluster has already collapsed into a magnetar, which could have easily emitted the FRB but would be too faint to see directly with JWST.
“Whether or not the association with the star is real, we’ve learned a lot about the burst’s origin,” Blanchard said. “If a double star system isn’t the answer, our work hints that an isolated magnetar caused the FRB.”
Putting RBFLOAT aside, this research shows that the newly upgraded CHIME experiment is capable of localizing elusive FRBs with unprecedented precision — and that JWST makes a powerful partner in the hunt for these mysterious space phenomena. Further tracking FRBs to their origins will not only help solve one of the biggest outstanding mysteries in astrophysics but could also shed new light on stellar dynamics, revealing how different stars behave over their bright-but-tumultuous lives.
