Scientists Pin Down the Farthest Fast Radio Burst Ever Seen

Astronomers have captured and pinpointed the most distant fast radio burst ever recorded, a millisecond-long flash of radio energy that has been travelling through space for more than ten billion years. The signal, catalogued as FRB 20240304B, was traced to a galaxy that formed roughly three billion years after the Big Bang, according to an international team led by researchers at the University of Sydney. The work was published in the journal Science.

The discovery more than doubles the distance of the previous record-holder. Fast radio bursts are intense pulses of radio waves that last only a fraction of a second but can briefly outshine entire galaxies in the radio part of the spectrum. Since the first one was detected in 2007, astronomers have logged hundreds of them, yet their origins remain one of the more stubborn puzzles in modern astrophysics.

Finding a burst is one thing; working out where it came from is another. The team combined two very different instruments to do both. South Africa’s MeerKAT radio telescope array, a network of dishes in the Karoo semi-desert, first caught the burst and narrowed its position in the sky. Then the James Webb Space Telescope, which observes in infrared from a vantage point about 1.5 million kilometres from Earth, looked at that patch and identified the faint host galaxy.

That pairing matters. Radio telescopes are good at catching the flash but poor at resolving exactly which galaxy produced it, because the signals are so brief and so far away. Webb’s sharp infrared eye can pick out extremely distant galaxies that would be invisible to most other observatories. Together they let the researchers match the burst to a specific galaxy, and then estimate its distance from the way the expansion of the universe has stretched the light on its journey.

Because radio waves travel through space, they pass through clouds of electrons scattered between galaxies. The more material a burst’s signal crosses, the more its arrival is smeared out in time. That makes distant bursts useful as probes of the thin, diffuse matter filling the space between galaxies — material that is otherwise almost impossible to map directly.

“This result is a step towards understanding where fast radio bursts come from and what they can tell us about the universe,” the researchers said, noting that the burst’s extreme distance makes it a valuable test of how much ordinary matter lies in the cosmic voids. Astronomers believe most bursts are produced by highly magnetised neutron stars known as magnetars, though the exact mechanism is still debated.

For now, the finding adds a far-flung data point to a small but growing sample. Each well-localised burst helps calibrate models of how matter is distributed across the cosmos. The team expects that next-generation radio facilities, with wider fields of view and greater sensitivity, will detect many more distant bursts — and perhaps push the record outwards again.