Fast radio bursts (FRBs) are remarkable cosmic phenomena, characterized by their brief yet intense emissions of radio waves. These bursts, which are believed to originate from compact celestial objects such as neutron stars and potentially black holes, last merely a thousandth of a second but can emit as much energy as entire galaxies.
Since the initial discovery of FRBs in 2007, astronomers have identified thousands of these bursts, with sources ranging from within our Milky Way galaxy to distances as staggering as 8 billion light-years away. Despite their frequency, the exact mechanisms behind these cosmic explosions remain largely unknown and the subject of ongoing debate.
Recently, a team of astronomers from MIT made a significant breakthrough by identifying the origins of at least one FRB using a cutting-edge approach. This groundbreaking research, published in the journal Nature, concentrated on FRB 20221022A, a fast radio burst detected from a galaxy approximately 200 million light-years away.
To pinpoint the exact location of this radio signal, the team analyzed a phenomenon known as “scintillation”—similar to the twinkling of stars seen from Earth. By examining variations in the brightness of the FRB, researchers concluded that this cosmic burst likely emanated from a region very close to its source, defying some prior models that suggested greater distances.
The findings suggest that FRB 20221022A originated from an area less than 10,000 kilometers away from a rotating neutron star—a distance comparable to that between New York City and Singapore. Given this proximity, scientists believe that the burst emerged from the neutron star’s magnetosphere, a high-magnetic environment surrounding the ultradense star.
This study marks the first compelling evidence that FRBs can originate from the magnetosphere of a neutron star. “In the frenetic environments surrounding neutron stars, magnetic fields reach extraordinary strengths,” explained Kenzie Nimmo, the study’s lead author and a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research. “There has been extensive debate about whether these bright radio emissions can escape the extreme plasma found in such environments.”
Kiyoshi Masui, an MIT associate professor of physics, elaborated: “Around magnetars, or highly magnetic neutron stars, atoms cannot exist; they are torn apart by the magnetic forces. This discovery is fascinating because it shows that the energy within these magnetic fields can twist and rearrange itself to emit radio waves that we can observe from halfway across the universe.”
Significance of FRB Research
In recent years, detections of fast radio bursts have surged, thanks in part to the Canadian Hydrogen Intensity Mapping Experiment (CHIME). This innovative radio telescope array comprises four large, stationary receivers designed to capture radio emissions specifically sensitive to FRBs.
Since its launch in 2020, CHIME has identified thousands of FRBs from various points in the universe. While it is widely accepted that these bursts originate from dense cosmic objects, the underlying physics is still unclear. Some theories suggest that FRBs arise from tumultuous magnetospheres, whereas others propose that they are products of shockwaves extending far from the central object.
To address these competing theories, researchers looked into scintillation—the distortion of light caused by the bending of waves as they pass through different media, like the gas present in galaxies. A critical clue in this research is that the degree of scintillation can reveal how far a burst is from its source; smaller scintillation indicates proximity to the origin.
Analyzing FRB 20221022A
The team focused their investigation on FRB 20221022A, which was detected by CHIME in 2022. This particular burst lasted approximately two milliseconds and had a moderate brightness. However, it exhibited a unique characteristic: the emitted light was highly polarized. This polarization demonstrated a smooth, S-shaped curve, indicative of a rotating emission source—a signature characteristic of pulsars, which are a type of highly magnetized neutron star.
To analyze this phenomenon, the team confirmed that scintillation occurred within the burst. They observed abrupt changes in brightness that indicated the FRB was indeed twinkling, leading them to conclude that gas in the burst’s host galaxy affected the radio waves. This natural lensing effect helped the researchers zoom in on the FRB’s origin, confirming that it emerged from a remarkably compact region, estimated at about 10,000 kilometers wide.
“This suggests that the FRB is likely from a location a mere few hundred thousand kilometers from its source,” noted Nimmo. “If it had come from a shockwave, the signal would likely have been millions of kilometers away, and we would have seen no scintillation at all.” Masui further emphasized the significance of their findings: “Zooming in to a 10,000-kilometer region from 200 million light-years away is like measuring the width of a DNA helix, about 2 nanometers, on the surface of the moon—a remarkable range of scales.”
The collaborative effort resulted in establishing that FRB 20221022A did not emerge from farther out but rather from the chaotic environment close to a neutron star, exemplifying the complex interactions at play around these extreme objects. “FRBs are constantly being produced, and CHIME detects several daily,” Masui remarked. “There’s considerable diversity in their origins, and this scintillation method will help clarify the various physical phenomena that drive these bursts.”
This pivotal research was funded by a consortium of institutions, including the Canada Foundation for Innovation, the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, and the Trottier Space Institute at McGill University.
Photo credit & article inspired by: Massachusetts Institute of Technology
