Discovery of the most distant fast radio burst
On 4 March 2024 the South‑African MeerKAT array caught a fleeting burst of radio waves that turned out to be unlike any previously recorded. The signal was stretched in time: low‑frequency components arrived much later than the high‑frequency ones, a hallmark of propagation through a vast column of tenuous intergalactic gas. This dispersion hinted that the burst originated from a truly remote corner of the cosmos.
Pinpointing the source with James Webb
Initial sky maps showed nothing at the burst’s coordinates, and even the powerful ground‑based observatories on Hawai‘i and Arizona recorded only darkness. The breakthrough came from the James Webb Space Telescope (JWST), which managed to glimpse a faint speck of light right next to the radio position. Statistical analysis gave a 97.5 % probability that the burst emanated from this tiny galaxy.
A galaxy from the infant universe
The identified galaxy is minuscule by modern standards, containing roughly ten million solar masses in stars. Yet it was undergoing a furious star‑formation episode: about 90 % of its stellar population was born within the 30 million‑year window preceding the burst. Because the light we see has travelled for almost 11 billion years, we are observing the galaxy as it looked when the universe was only about three billion years old.
What powered the flash?
Fast radio bursts (FRBs) are millisecond‑long eruptions of radio energy, and their exact origins remain a puzzle. In this case, the environment points toward a magnetar – a highly magnetised neutron star left behind after a massive star’s death. Magnetars are expected to appear in regions of recent star formation, exactly where this galaxy’s youthful stars reside. Independent experts, such as Prof. Joeri van Leeuwen of Leiden Observatory, note that the measured dispersion matches the distance derived from JWST, strengthening the link between the burst and the distant galaxy.
Why the discovery matters
Beyond setting a new distance record – surpassing the previous 8‑billion‑year FRB – the event offers a novel probe of the otherwise invisible intergalactic medium. As the radio waves traversed the sparse gas, they acquired a characteristic delay pattern that encodes the density and composition of the material they crossed. By analysing such patterns from ever‑more distant bursts, astronomers can map the distribution of “missing” baryonic matter across cosmic time.
Moreover, the detection demonstrates the synergy between radio facilities and cutting‑edge infrared observatories. Without JWST’s unprecedented sensitivity, the host galaxy would have remained hidden, and the burst’s true significance would have been lost.
Future surveys with MeerKAT, the upcoming Square Kilometre Array, and space‑based telescopes promise to uncover many more ancient FRBs, turning these brief flashes into powerful time machines that let us watch the universe’s formative epochs unfold.
