Webb Traces the Farthest Fast Radio Burst to a Tiny Galaxy
On 4 March 2024, a flash of radio waves lasting a fraction of a second reached a telescope in South Africa. It had traveled for most of the age of the universe. Finding where it came from took the James Webb Space Telescope, and the answer surprised the team: not a big galaxy, but a tiny one.
The most distant fast radio burst so far
Fast radio bursts, or FRBs, are brief, powerful pulses of radio waves from deep space. The MeerTRAP team caught this one, FRB 20240304B, with the MeerKAT radio telescope. Radio data hinted that it came from very far away, but the largest ground-based telescopes could not see any galaxy at its position.
Webb’s NIRCam camera spotted the faint host galaxy, and its NIRSpec instrument measured a redshift of 2.148. That puts the burst at about 3 billion years after the Big Bang. ESA calls it the most distant FRB found so far. Most known FRBs went off billions of years later in cosmic history.
A tiny galaxy in a hurry
The host is a small dwarf galaxy, about 1,000 times less massive than the galaxies astronomers expected. It existed during “cosmic noon,” the era when star formation across the universe peaked, and it was actively making stars. Its star formation rate suggests most of its stars may have formed within about 30 million years.
A clue to what makes these bursts
Astronomers still debate what produces FRBs. One leading idea points to magnetars, neutron stars with extremely strong magnetic fields that can form soon after a massive star explodes as a supernova. Another points to mergers of neutron stars, which take billions of years to happen.
A young, small, fast-growing host fits the magnetar idea much better. “Our work suggests that it’s very unlikely that this FRB was produced by a merger,” said lead author Manisha Caleb of the University of Sydney.
The burst carried one more bonus. On its way to Earth, its signal picked up traces of a previously unknown galaxy cluster at redshift 0.3 and of the nearby Virgo Cluster.
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