Webb and MeerKAT Find the Most Distant Fast Radio Burst Yet, From a Small Galaxy About 11 Billion Years Back

A flash that lasted a few thousandths of a second has become the most distant fast radio burst yet found. The burst, catalogued as FRB 20240304B, was detected by South Africa's MeerKAT telescope on 4 March 2024. A team led by Manisha Caleb of the University of Sydney reports in Science that its light travelled for roughly 11 billion years to reach us, according to Sky and Telescope.

In those few milliseconds the burst released more energy than the Sun does in a year. It left its source when the universe was about 3 billion years old, at a redshift of 2.15, and the finding was published on 8 October.

How far is it, and how does that compare with the 2023 record?

In 2023 ESO announced FRB 20220610A, which Australia's ASKAP telescope had detected in June 2022, as the most distant burst then known, with light from its source galaxy that had taken about eight billion years to arrive. The new burst's light-travel time is roughly 11 billion years, which puts it well beyond that mark.

Why did it take the Webb telescope?

MeerKAT, an array of 64 radio dishes in South Africa, detected the burst and pinned it to a patch of sky near the star Denebola in Leo. Archival images and ground-based telescopes, including Keck in Hawaii and the MMT in Arizona, found no galaxy at that position. The James Webb Space Telescope did. Its Near-Infrared Camera picked up a very faint host, and its Near-Infrared Spectrograph measured the redshift, according to Sky and Telescope and to OzGrav.

A small galaxy, and a clue about where bursts come from

The host surprised the team. It is a dwarf galaxy that is still forming stars, about a thousand times less massive than expected for a typical burst host, and OzGrav says most of its stars may have formed within about 30 million years. Caleb said the team had expected a big, well-formed galaxy, and "instead it was a little dwarf galaxy".