The most distant known fast radio burst came from a small galaxy actively making stars, observations with the James Webb Space Telescope show. The signal dates to when the universe was about 3 billion years old. The researchers published the findings in Science on October 8, 2026.
Fast radio bursts are flashes of radio waves lasting only milliseconds. Their origins remain uncertain. Finding the galaxy behind a burst helps researchers test whether its source fits a young stellar population or a much older one.
South Africa's MeerKAT telescope detected this burst on March 4, 2024, giving it the name FRB 20240304B. Ground-based telescopes could not see a galaxy at its precisely measured position. Webb's near-infrared camera found the host, and its spectrograph measured a redshift of 2.148.
Redshift measures how much expanding space stretches light. In this case, it corresponds to a lookback time of more than 10.7 billion years, according to Paris Observatory-PSL. The host's stellar mass is about a thousand times smaller than is typical for previously observed FRB hosts.
That young, star-forming environment supports an origin involving a magnetar, a highly magnetic neutron star. The researchers argue that a merger of two neutron stars is less likely here because such pairs generally take much longer to merge. The result supports a proposed explanation; it does not settle the origin of every burst.
The signal also carried evidence of matter along its journey. The team identified signatures of a previously unknown galaxy structure and the nearby Virgo Cluster. Radio bursts can probe intervening matter as well as their sources. This brief flash records a long route through space.
