On October 10, 2024, the South African Radio Astronomy Observatory (SARAO) announced that the parent galaxy of FRB 20240304B—the most distant fast radio burst ever found—had been pinpointed using NASA’s James Webb Space Telescope and South Africa’s MeerKAT radio telescope. Traveling for over 10 billion years, the millisecond-long radio flash originated from a tiny, star-forming dwarf galaxy when the universe was roughly a quarter of its current age.
First discovered in 2007, fast radio bursts remain enigmatic, millisecond-long flashes of high-energy radio emission from the distant universe. Their exact origin has stayed uncertain largely because most are observed just once and never repeat. The breakthrough regarding FRB 20240304B, detected initially on March 4, 2024, came from the MeerTRAP team, an international collaboration utilizing the MeerKAT telescope array to capture transient radio signals.
Locating the Distant Signal with MeerKAT and Webb
The MeerKAT telescope precisely localized the burst, indicating an extreme distance, but ground-based telescopes could not detect the faint host galaxy. To measure the distance accurately, the research team turned to NASA’s James Webb Space Telescope. Utilizing Webb’s NIRCam (Near-Infrared Camera), the astronomers detected the host galaxy and measured a redshift of 2.148.
The resulting data proved that the radio wave traveled for more than 10 billion years before hitting Earth. This event occurred during an era when the universe was only about 3 billion years old. This finding more than doubles the previous distance record for fast radio bursts.
Beyond breaking distance records, the signal provided a unique probe of intermediate space. The team found the imprint of two cosmic structures along the signal’s path: a previously unknown galaxy cluster at a redshift of 0.3, roughly 3.5 billion light-years away, and the nearby Virgo Cluster, situated about 54 million light-years from Earth.
Dwarf Galaxy Origins Challenge Existing Merger Theories
The characteristics of the host galaxy surprised the researchers. While most previously studied fast radio bursts originate in massive star-forming galaxies, the host of FRB 20240304B was 1,000 times less massive than expected.
“We thought it would be a big, nicely formed galaxy with lots of stars, and instead it was a little dwarf galaxy, although it was actively forming stars,” Manisha Caleb of the University of Sydney, lead author of the study published in the journal Science, stated in a release.
Observations showed the galaxy existed during “cosmic noon,” a peak era of universal star formation. The galaxy’s rapid star formation rate suggested that the majority of its stars may have formed within a span of just 30 million years. This specific evolutionary timeline heavily influences theories regarding what triggers the bursts.
Traditionally, scientists have debated two main possibilities: the collision of a pair of neutron stars, or a solitary, youthful neutron star endowed with an intensely powerful magnetic field, which is referred to as a magnetar. Binary neutron stars typically take at least a billion years to merge, making that scenario mathematically improbable for a galaxy active in the early universe. “Our work suggests that it’s very unlikely that this FRB was produced by a merger,” Caleb noted.
Consequently, researchers point toward an energetic single-star event, such as a starquake in a young magnetar born from the collapse of a massive star. Co-author Themiya Nanayakkara of the University of Sydney emphasized Webb’s capacity to push observational boundaries beyond previous limits. Matthew Bailes of Swinburne University described the study as confirmation of how powerful these bursts are as cosmological tools.
Future Prospects for Early Universe Radio Astronomy
Astrophysicist Sarah Webb, who was not part of the research team, noted that the finding suggests such signals were likely very common in the early universe. Dr. Kaustubh Rajwade of the Department of Physics at the University of Oxford, who helped develop the localization software, highlighted that MeerKAT is uniquely positioned to find fast radio bursts at extreme distances. The research team estimates that MeerKAT could detect and localize a few such bursts annually, reaching more than halfway back to the beginning of the universe.
Despite these advancements, crucial questions remain open. It is not yet known whether FRB 20240304B will ever repeat its signal, and a single observed galaxy does not prove how common such dwarf hosts are across the early cosmos. Magnetars remain a leading theoretical explanation, but definitive proof of the exact engine driving these millisecond flashes awaits further observation.
