Fast radio bursts (FRBs) are brief, brilliant explosions of radio waves emanating from compact objects, such as neutron stars and possibly black holes. While lasting only a thousandth of a second, these bursts can shine so brightly as to outshine whole galaxies for that instant. Since the first FRB was discovered in 2007, astronomers have found thousands from our galaxy to 8 billion light-years away. Yet, it is not clear what precisely causes these cosmic radio flares.
Now, a team of astronomers from MIT has pinpointed the origin of one such fast radio burst using a novel technique that could be applied to other FRBs. In their study, the team focused on FRB 20221022A, detected from a galaxy 200 million light-years away.
By analyzing the FRB’s “scintillation”—the twinkling effect similar to stars in the night sky—they determined that the burst came from close to its source, not from a distant location as previously theorized.
The team estimates that FRB 20221022A erupted from a location only 10,000 kilometers away at most from a rotating neutron star. That is less than the distance between New York and Singapore. The burst probably originated within the neutron star’s magnetosphere at that proximity—a strongly magnetic area around the ultracompact star.
The team’s results offer the first definitive proof that a fast radio burst can come from the magnetosphere, the strongly magnetic region just outside an ultracompact object.
Lead author Kenzie Nimmo, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research, said, “In these environments of neutron stars, the magnetic fields are really at the limits of what the universe can produce. There’s been a lot of debate about whether this bright radio emission could escape from that extreme plasma.”
Kiyoshi Masui, an associate professor of physics at MIT, said, “Around these highly magnetic neutron stars, also known as magnetars, atoms can’t exist—they would just get torn apart by the magnetic fields. The exciting thing is that the energy stored in those magnetic fields, close to the source, is twisting and reconfiguring such that it can be released as radio waves that we can see halfway across the universe.”
Since 2020, CHIME has detected thousands of fast radio bursts (FRBs) from across the universe. While scientists agree that these bursts originate from extremely compact objects, the exact mechanisms driving them remain unclear. Some models suggest that FRBs arise from the turbulent magnetosphere surrounding a compact object, while others propose that they come from shockwaves propagating much farther out.
To distinguish between these possibilities, the team used scintillation—the effect where light from a small, bright source, like a star, appears to twinkle as it passes through a medium such as a galaxy‘s gas. The smaller or farther away the object, the more it twinkles; larger or closer objects, like planets, experience less bending and don’t twinkle.
The researchers hypothesized that by measuring the degree of scintillation in an FRB, they could estimate the size of the region from which it originated. A smaller region would suggest the burst came from near the source, likely within a magnetically turbulent environment. A larger region would support the idea that the burst came from distant shockwaves.
To determine the origin of fast radio bursts (FRBs), the team used scintillation—the effect where light from a small, bright source, like a star, bends as it passes through a medium such as a galaxy’s gas, making the star appear to twinkle. The smaller or farther away the object, the more it twinkles. Larger or closer objects, like planets in our solar system, experience less bending and do not twinkle.
The team hypothesized that by measuring the degree of scintillation in an FRB, they could estimate the size of the region from which it originated. A smaller region would indicate the burst came from close to its source, likely within a magnetically turbulent environment. A larger region would suggest the burst came farther away, supporting the theory that FRBs result from distant shockwaves.
To test their hypothesis, the researchers focused on FRB 20221022A, a fast radio burst detected by CHIME in 2022. This burst, which lasted about two milliseconds, was typical in brightness. However, the team’s collaborators at McGill University discovered a unique feature: the light from the burst was highly polarized, with the polarization angle following a smooth S-shaped curve. This pattern is interpreted as evidence of rotation at the emission site—previously observed in pulsars, which are rotating, magnetized neutron stars.
This unusual polarization in FRB 20221022A suggested that the signal likely originated from the immediate vicinity of a neutron star, marking a significant first in FRB research.
Nimmo said, “The FRB is probably hundreds of thousands of kilometers from the source. That’s very close. For comparison, we would expect the signal to be more than tens of millions of kilometers away if it originated from a shockwave, and we would see no scintillation.”
Masui said, “Zooming into a 10,000-kilometer region, from a distance of 200 million light years, is like being able to measure the width of a DNA helix, which is about 2 nanometers wide, on the surface of the moon. There’s an amazing range of scales involved.”
The team’s results, combined with those of the McGill team, paid to the suggestion that FRB 20221022A came from the outer regions of a compact object. Instead, the study confirms for the first time that fast radio bursts can originate from very near a neutron star, within highly turbulent magnetic environments.
“These bursts occur constantly, and CHIME detects several each day,” says Masui. “There may be considerable diversity in how and where they happen, and this scintillation method will be invaluable for understanding the various physical processes driving these bursts.”
Several institutions, including the Canada Foundation for Innovation, the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, the Canadian Institute for Advanced Research, the Trottier Space Institute at McGill University, and the University of British Columbia supported this research.
Journal Reference:
- Mckinven, R., Bhardwaj, M., Eftekhari, T. et al. A pulsar-like polarization angle swing from a nearby fast radio burst. Nature 637, 43–47 (2025). DOI: 10.1038/s41586-024-08184-4