In the vast expanse of the universe, brief and powerful flashes of radio waves occasionally pierce the cosmic silence, originating from billions of light-years away. These phenomena, known as Fast Radio Bursts (FRBs), are intense pulses of radio-frequency emissions that last mere milliseconds but release energy equivalent to what the Sun emits over several days. First detected less than two decades ago, FRBs have captivated astronomers, offering clues about extreme astrophysical processes and the structure of the cosmos itself. Despite thousands of detections, their exact origins remain elusive, with recent discoveries challenging long-held assumptions and sparking new theories.
The Discovery of FRBs: A Serendipitous Find
The story of FRBs began in 2007 when astronomers Duncan Lorimer and his student David Narkevic analyzed archival data from the Parkes radio telescope in Australia. They uncovered a single, intense burst recorded in 2001, now called the Lorimer Burst (FRB 010724), which lasted less than 5 milliseconds and appeared to come from outside our galaxy. Initially met with skepticism—some thought it might be terrestrial interference—the signal’s extragalactic nature was confirmed by its high dispersion measure, a sign it had traveled through vast amounts of ionized plasma in space.
Live detections followed in 2015, and the floodgates opened with the advent of advanced telescopes like the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which began operations in 2018. By June 2021, CHIME had reported over 500 FRBs in a single year. The first FRB from within our Milky Way, FRB 200428, was detected in April 2020, linking it to a magnetar—a highly magnetized neutron star—providing the first solid clue to their potential sources.
Characteristics of These Cosmic Flashes
FRBs are defined by their brevity and brightness. They span radio frequencies from 400 MHz to 8 GHz, appearing as broadband flashes that are unresolved and isotropic, meaning they don’t cluster along the Milky Way’s plane but come from all directions in the sky. Most are one-off events, but about 3% repeat, like FRB 121102, which has emitted over 300 bursts and shows a 157-day periodicity.
Their signals are dispersed by intergalactic electrons, allowing astronomers to use FRBs as probes for “missing” cosmic matter—the diffuse baryons that make up about half of the universe’s normal matter but are hard to detect otherwise. Some exhibit unique quirks, such as the “slide whistle” pattern in a 2023 detection, where the frequency swept downward like a musical note.
Theories on What Causes FRBs
The origins of FRBs are a hotbed of speculation. Leading candidates include magnetars, whose extreme magnetic fields could generate the bursts through flares or starquakes. Evidence from FRB 200428, associated with the Milky Way magnetar SGR 1935+2154, supports this. Other ideas involve neutron star mergers, black hole interactions, or even exotic physics like axion miniclusters or cosmic strings.
Repeating FRBs might stem from different mechanisms than one-offs, perhaps involving binary systems where a magnetar interacts with a companion star. Plasma-based emissions, such as synchrotron maser from relativistic shocks, are proposed for the radio waves themselves. Terrestrial explanations, like microwave oven interference (known as perytons), have been ruled out for true FRBs.
Recent Breakthroughs: Challenging Assumptions
2025 has been a pivotal year for FRB research. In January, astronomers traced FRB 20240209A to the outskirts of an ancient, “dead” elliptical galaxy 2 billion light-years away—a massive, star-formation-quenched behemoth over 11 billion years old. This location defies expectations, as magnetars form from young, massive stars, which shouldn’t exist in such old galaxies. It suggests FRBs might arise in globular clusters of ancient stars or through entirely new processes.
In March 2025, an extraordinarily powerful FRB, dubbed RBFLOAT (Radio Brightest FLash Of All Time), was detected by CHIME. This burst, from the spiral galaxy NGC 4141 about 130 million light-years away, released energy equal to the Sun’s four-day output in under a second. Pinpointed to a 45-light-year region near a star-forming area, it was localized with unprecedented precision using CHIME’s new outriggers. Follow-up with the James Webb Space Telescope revealed a faint infrared source, possibly a red giant or massive star linked to a neutron star companion. Experts like Amanda Cook from McGill University called it a “turning point,” potentially revealing whether FRBs come from dying stars or exotic magnetic objects.
On August 26, 2025, reports confirmed RBFLOAT as the brightest FRB yet, further emphasizing its role in reshaping theories. Other 2025 findings include FRB 20240114A, a hyper-active repeater in a galaxy cluster, associated with gamma-ray emissions.
Implications and the Road Ahead
FRBs are more than curiosities; they map the universe’s hidden matter and test fundamental physics. As telescopes like CHIME, ASKAP, and the upcoming Square Kilometre Array come online, detections will surge, potentially resolving whether all FRBs repeat or if distinct classes exist. These signals from deep space remind us that the universe still holds significant mysteries, waiting to be decoded.
