Webb traces most distant fast radio burst to tiny galaxy

Astronomers have traced a radio flash that lasted only milliseconds to a small, faint galaxy that existed when the universe was about 3 billion years old. The burst, FRB 20240304B, is now the most distant fast radio burst with an identified host galaxy, and the findings appear in the journal Science.zmescience+1

The record matters for two reasons. The dwarf host galaxy was forming stars quickly, which supports the idea that these flashes come from young magnetars and not from older neutron-star mergers. The burst also offers a way to study the gas that lies between galaxies across most of cosmic history.heise+2

From MeerKAT to Webb

The MeerTRAP team found the burst on March 4, 2024, using the MeerKAT radio telescope in South Africa, which is where its name comes from. The radio data suggested the source was very far away. Ground-based telescopes could see nothing at the burst's position because the galaxy was too faint.ground+2

The James Webb Space Telescope's NIRCam camera found a small galaxy at that spot. Its NIRSpec spectrograph then measured a redshift of 2.148, which puts the galaxy in the era called "cosmic noon," when star formation across the universe was at its peak. The burst is more than twice as distant as the previous record-holder.diyphotography+2

A young, metal-poor host

The galaxy has a mass about 10 million times that of the Sun. The team says that is roughly 1,000 times less than expected. About 90% of its stellar mass formed in the past 30 million years.zmescience+2

"The galaxy hosting this burst is surprisingly small, metal-poor and undergoing a very active episode of star formation," said co-author Laura Driessen of the University of Sydney. Lead researcher Manisha Caleb, also of the University of Sydney, called it "an extraordinary glimpse into the distant universe".zmescience

Heise reported that stars that young conflict with theories in which bursts need billions of years to develop, as they would for merging neutron stars. A magnetar, a neutron star with an extremely strong magnetic field, could form and flare within millions of years. Heise also noted that an earlier burst traced to an old, "dead" elliptical galaxy did not fit the magnetar picture. That suggests there may be more than one way these bursts form, and the team cautions that not all of them share the same origin.heise+2

Probing the cosmic web

As the signal traveled, it passed through ionized gas, including traces from an unknown group of galaxies and from the Virgo Cluster. Researchers say distant bursts like this one could help map charged matter across about 80% of cosmic history. Host galaxies have been confirmed for about 100 bursts so far. The team expects MeerKAT to find several bursts a year from the first half of the universe's history, with Webb studying their host galaxies.ua+2