The origin of a sparkling Fast Radio Burst (FRB) has been discovered in a galaxy 200 million light years away through the work of MIT astronomers.
FRBs are quick yet brilliant bursts of radio waves sent forth from neutron stars and black holes. Since the 2007 discovery of the first FRB, unraveling the phenomenon has remained a focal point for many astronomers.
The MIT team focused on FRB 20221022A, discovered in 2022 by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Since beginning operations in 2017, CHIME has detected thousands of FRBs and has played an instrumental role in filling out the FRB picture. The radio telescope’s four large, half-pipe-shaped receivers are tuned to the range typical for FRBs.
The FRB 20221022A signal has a two-millisecond duration and is fairly standard. However, the MIT team’s McGill University collaborators noticed one strange element of the FRB: It was highly polarized with an S-shaped polarization curve. They interpreted this to mean the emission site is rotating, something observed in highly magnetized stars like magnetars and pulsars.
Answers In Twinkling Stars
Scientists believe that extremely compact objects are generating the FRBs, but beyond that the physics remains murky. Some models indicate that FRBs originate within shockwaves emanating from an object, while others place the origination within the magnetosphere closer to the object. The star’s scintillation, the technical term for its sparkle, provided the information the astronomers needed to determine which model best fit FRB 20221022A.
Light filtering through another medium, like gas, generates the scintillating effect. From a distant vantage point, that scintillating effect makes a star appear to twinkle. Light coming off of closer and larger objects bends far less and, therefore, doesn’t twinkle so much. From this knowledge, the team hypothesized estimating the degree of twinkle would, in turn, provide the data needed to determine the relative size of the origination region.
A smaller region would indicate close proximity of the burst and its source and a high likelihood of a magnetically turbulent environment, while a larger region would indicate a farther burst, supporting the shockwave model.
Sparkling Fast Radio Bursts
By studying the burst’s brightening and dimming, the MIT team discovered that it originated near its source rather than further out, as some previous models suggested. The astronomers analyzed CHIME data and honed in on dramatic oscillations in brightness to interpret that as scintillation. This confirmed gas exists between CHIME’s point of view and the FRB, as only gas would create the light-bending effect. They then determined the gas’s location, placing the burst origin within a small region about 10,000 kilometers wide.
“Zooming in to 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,” co-author Kiyoshi Masui says says. “There’s an amazing range of scales involved.”
Magnetic Origins OF FAST RADIO BURSTS
This small origination likely signals that the distance the FRB exploded from a rotating star is within hundreds of thousands of kilometers of the source object, a minute distance on a cosmic scale. A shockwave-born FRB would be tens of millions of kilometers away from its source and lack scintillation. That close range indicates that the FRB probably came from the star’s magnetosphere, the region where the magnetic field is dominant.
The MIT team’s findings represent the first conclusive evidence that an FRB can originate from a magnetosphere.
“In these environments of neutron stars, the magnetic fields are really at the limits of what the universe can produce,” says lead author Kenzie Nimmo. “There’s been a lot of debate about whether this bright radio emission could even escape from that extreme plasma.”
“These bursts are always happening, and CHIME detects several a day,” Masui says. “There may be a lot of diversity in how and where they occur, and this scintillation technique will be really useful in helping to disentangle the various physics that drive these bursts.”
The paper “Magnetospheric Origin of a Fast Radio Burst Constrained Using Scintillation” appeared on January 1, 2025 in the Nature.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.