Astronomers using the MeerKAT radio telescopes in South Africa and NASA’s James Webb Space Telescope have pinpointed the host galaxy of the most distant fast radio burst ever detected — a millisecond flash, designated FRB 20240304B, that has been travelling for more than ten billion years and originated when the universe was about three billion years old, according to the study published in Science. The burst was first detected in 2024; identifying the galaxy it came from required Webb’s infrared reach.
Fast radio bursts are among astronomy’s standing mysteries: flashes brighter than galaxies that last thousandths of a second and then, usually, never repeat. Finding one at this distance does double duty. It tests what produces them — the leading suspect is the magnetar, a young neutron star with a magnetic field of almost unreasonable strength — and it turns the burst into a probe, since the signal’s distortion on its ten-billion-year journey records the gas and matter it passed through on the way.
The host galaxy held a surprise: it is a tiny dwarf galaxy, roughly a thousand times less massive than expected, and busy forming stars. That profile fits the magnetar theory, since magnetars are born in the deaths of massive young stars — and a small, furiously star-forming galaxy in the early universe is exactly where such stars lived and died in numbers.
The intergalactic part of the result may last longest. As the burst crossed most of cosmic history, it illuminated the reservoirs of ordinary matter strung between galaxies — matter that census-taking astronomers have historically struggled to account for. Each precisely located burst adds a line to that ledger.
Records in this field now fall regularly. What endures is the technique: radio telescopes to catch the flash, Webb to find its home, and a millisecond of light doing the work of a lantern across ten billion years.
The result also sharpens the design brief for the next generation of radio observatories. Bursts at redshift 2 are detectable now only because MeerKAT’s sensitivity caught a bright one; a fuller census of the early universe’s bursts awaits the Square Kilometre Array and its peers, which will catch such flashes routinely and localize them to their hosts in real time. Each will be another lantern. The ledger of the universe’s ordinary matter — long embarrassingly incomplete, with baryons theorized but uncounted — is being balanced one millisecond at a time. FRB 20240304B’s contribution is to prove the accounting works across nearly the whole of cosmic time: the flash found its galaxy, and the galaxy, against expectation, was a dwarf with a story to tell.
