Brightest fast radio burst ever detected could help solve an enduring cosmic mystery

Astronomers have spotted the brightest fast radio burst yet coming from a nearby galaxy. Observations of this phenomenon, a powerful flash of radio waves that lasts only about a millisecond, could shed light on one of the most mysterious cosmic phenomena ever studied.

Fast radio bursts, or FRBs, were first discovered in 2007, but their exact sources remain unknown. Since their identification, astronomers have been tracing the bursts’ origin in the hopes of gathering clues about what unleashes them and sends them across the cosmos.

Astronomers observed FRB 20250316A, nicknamed “RBFLOAT” for “Radio Brightest FLash Of All Time,” on March 16.

The signal was traced to the galaxy NGC 4141 about 130 million light-years away from Earth. The details of the detection, made with the FRB-hunting Canadian Hydrogen Intensity Mapping Experiment, or CHIME, and its newly operational, smaller array of telescopes, called Outriggers, were published Thursday in The Astrophysical Journal Letters.

“With the CHIME Outriggers, we are finally catching these fleeting cosmic signals in the act — narrowing down their locations not only to individual galaxies, but even to specific stellar environments,” said lead study author Amanda Cook, a Banting postdoctoral fellow at the Trottier Space Institute and Physics Department at McGill University, in a statement.

After the burst was detected, scientists used the James Webb Space Telescope to zoom in on where it originated. The observations add evidence to a leading theory that magnetars, or the highly magnetized remnants of dead stars, could be a source of fast radio bursts. A study about Webb’s follow-up observations was also published on Thursday in The Astrophysical Journal Letters.

“This was a unique opportunity to quickly turn JWST’s powerful infrared eye on the location of an FRB for the first time,” said Peter Blanchard, lead author of the Webb study and research associate in the Harvard College Observatory at the Center for Astrophysics | Harvard & Smithsonian, in a statement. “And we were rewarded with an exciting result — we see a faint source of infrared light very close to where the radio burst occurred. This could be the first object linked to an FRB that anyone has found in another galaxy.”

The new insights from both studies could also be used to help astronomers solve another key mystery surrounding fast radio bursts by determining whether they have a repetitive pattern, like a cosmic heartbeat, or whether there are different flavors of radio bursts that release a singular bombastic signal before falling silent.

A CHIME in the nick of time

The CHIME radio telescope near Penticton, British Columbia, at the Dominion Radio Astrophysical Observatory, has enabled astronomers for the past seven years to spot thousands of fast radio bursts when they arrive at Earth after traveling across the cosmos.

Work was completed earlier this year to get Outriggers up and running at sites in British Columbia, West Virginia and California with the goal of tracing fast radio bursts to their specific locations with enhanced precision. The Outriggers combine pinpointing capabilities with a large field of view, said Wen-fai Fong, coauthor on the CHIME study and associate professor of physics and astronomy at Northwestern University’s Weinberg College of Arts and Sciences.

Astronomers had their chance to test the array’s “game-changing” capabilities in March, just a couple of months after the Outriggers came online, Fong said.

The RBFLOAT released as much energy as the sun produced in four days — but in less than a second.

The Outrigger telescopes enabled the team to pinpoint the fast radio burst’s point of origin to a region measuring about 45 light-years across, an area smaller than a cluster of stars. The precision of the location is like spotting a quarter from about 100 kilometers (62 miles) away, Cook said.

Prior to the Outrigger telescopes’ capability to triangulate a fast radio burst to its source, “it was like talking to someone on the phone and not knowing what city or state they were calling from,” said study coauthor Bryan Gaensler, dean of the University of California, Santa Cruz science division.

“Now we know not only their exact address, but which room of their house they’re standing in while they’re on the call.”

Zooming in on a galactic arm

Follow-up observations made with the 6.5-meter MMT telescope in Arizona and the Keck II telescope’s Cosmic Web Imager in Hawaii revealed that RBFLOAT came from the spiral arm of a galaxy, which is full of star-forming regions. But it originated near, and not inside, a star-forming region.

Some previous fast radio bursts appear to have come from magnetars, or highly magnetized rotating neutron stars that release radio waves. Scientists have long hypothesized that neutron stars, ultradense core remnants left behind after massive stars explode, might be the origin of fast radio bursts.

Magnetars typically form when gravity triggers a gigantic star to collapse on itself. And star-forming regions are where young magnetars can be found.

The fact that the burst was traced to a region outside a star-forming clump could suggest that the “magnetar was kicked from its birth site or that it was born right at the FRB site and away from the clump’s center,” said study coauthor Yuxin (Vic) Dong, graduate student and National Science Foundation Graduate Research Fellow in the department of physics and astronomy at Northwestern University.

Webb’s powerful gaze

Blanchard’s team used the Webb telescope to search for a signal in infrared light that may have originated at the same cosmic location as RBFLOAT.

Webb’s data revealed an object, named NIR-1, which could be a massive star or a red giant — a sun-like star at the end of its life that has brightened significantly. Neither star is considered a candidate for the direct cause of a fast radio burst. But an unseen companion like a neutron star could be siphoning material away from the larger star — and that may have been enough to release a burst of radio waves, Blanchard said.

It’s also possible that the infrared light that Webb detected was a reflection of a flare caused by the same object that released the radio burst, such as a magnetar.

“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.”

To repeat or not to repeat

Studying the immediate surroundings where both repeating and non-repeating fast radio bursts occur can help astronomers determine what causes the signals to repeat in the first place, Fong said.

While many fast radio bursts are known to repeat pulsations over several months, the RBFLOAT did not release any repeat signals in the hundreds of hours after it was initially observed.

RBFLOAT is the first non-repeating burst to be localized to such precision, said Sunil Simha, coauthor on the CHIME study and a Brinson postdoctoral fellow at Northwestern University’s Center for Interdisciplinary Exploration and Research in Astrophysics and the University of Chicago’s Astronomy and Astrophysics Department.

“Since this represents the first non-repeating FRB with its local environment fully mapped out, it remains to be seen if others will follow suit, or if this was an oddball,” Fong said.

The results of both studies provide insight into the question of whether all fast radio bursts eventually repeat, said Liam Connor, assistant professor of astronomy at Harvard University. Connor has studied the phenomenon before but was not involved in either study.

“Before detecting FRB 20250316A, CHIME had been unknowingly monitoring the source every day for seven years, because CHIME sees the whole Northern Sky once per day,” Connor wrote in an email. “Somehow, zero bursts were detected in thousands of transits, until one of the brightest events of all time suddenly went off. If all FRBs are repeaters, then clearly some are extremely sporadic and unpredictable.”

Previously, cataclysmic theories, like the collision of massive objects, have been ruled out for repeating fast radio bursts since the source would be destroyed while producing the first burst, Dong said.

“We can reopen the door to those more explosive theories for RBFLOAT and its kin,” she said.

Simha wants to build a database that shows where fast radio bursts have originated, which could reveal what may be responsible for creating them — and if they are all created equally. More data could show if there are multiple ways to produce fast radio bursts, Blanchard said.

The CHIME telescope and its Outriggers continue monitoring the sky to see whether other non-repeating fast radio bursts release another signal. The telescope array is anticipated to help localize hundreds of fast radio bursts a year. And the team will continue to monitor RBFLOAT in case it has another outburst.

“Alternatively, maybe we never detect another burst from this source, and start to see additional seemingly one-off bursts, potentially in similar environments,” Cook wrote in an email. “Then we’re trying to solve the mysteries of the origins of at least two different populations. In either case, we are really excited to uncover the mysteries the universe has in store for us.”

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