Astronomers have traced a split-second burst of radio energy back to a faint, star-forming dwarf galaxy roughly 10.6 billion light-years away, making it the most distant fast radio burst ever pinpointed and more than doubling the previous distance record, according to a study published Oct. 8 in the journal Science.
The burst, catalogued as FRB 20240304B, was first caught in March 2024 by the MeerTRAP survey using South Africa's MeerKAT radio array, which localized it precisely enough on the sky to hunt for a host galaxy. The trouble was that nothing showed up — not even in images from some of the largest ground-based telescopes. Researchers then won time on the James Webb Space Telescope, whose NIRCam imager and NIRSpec spectrograph finally identified a faint galaxy at the burst's location and measured its redshift at 2.148, corresponding to a lookback time of roughly 10.6 billion years — light that left its source when the universe was only about 3 billion years old.
A surprisingly small, young galaxy
What startled the research team was the host itself: a dwarf galaxy with only a small fraction of the Milky Way's stellar mass, poor in heavy elements and in the midst of an intense burst of star formation. That combination is notable because fast radio bursts — millisecond flashes that can release as much energy as the sun emits in a year — are widely suspected to come from magnetars, the ultra-magnetized remnants of massive stars. A young, actively star-forming galaxy is exactly the kind of environment where such remnants would be expected to form, and a release from the Observatoire de Paris, whose astronomers contributed to the analysis, frames the finding as supporting a magnetar origin.
That link remains an inference, not a direct detection — no object has actually been seen flaring at the burst's location, and researchers caution that the galaxy's characteristics are circumstantial evidence for the magnetar hypothesis rather than proof of it. Other proposed sources of fast radio bursts, including mergers of neutron stars, have not been ruled out for this event.
The discovery also pushes the study of these bursts into a new epoch: FRB 20240304B is the first localized at the "cosmic noon" era, when star formation across the universe was near its peak, offering a potential new tool for probing matter in the vast spaces between galaxies. Follow-up observations, including deeper Webb spectroscopy and continued monitoring by MeerKAT for repeat bursts from the same source, are expected to test whether the galaxy's young stellar population can be more directly tied to a magnetar remnant — and whether even more distant bursts can be found and localized the same way.
