Astronomers detect most distant fast radio burst, just 3 billion years after Big Bang
Tomasz Nowakowski
astronomy writer
Robert Egan
associate editor
Using the MeerKAT radio telescope, an international team of astronomers have discovered a new fast radio burst, which received designation FRB 20240304B. The measured redshift of FRB 20240304B indicates that it is the most distant fast radio burst known to date. The finding was reported in a research paper August 3 on the arXiv pre-print server.
Fast radio bursts (FRBs) are intense flashes of radio emission that last only a few milliseconds and showcase the characteristic dispersion sweep of radio pulsars. To date, the physical nature of this mysterious phenomenon remains unknown; however, astronomers consider a variety of explanations ranging from synchrotron maser emission from young magnetars in supernova remnants to cosmic string cusps.
The vast majority of FRBs have been detected at relatively low redshifts of below 0.5. Therefore, their distribution at higher redshift is still poorly studied. That is why astronomers are especially interested in finding new high-redshift FRBs, as they can offer important clues about galaxy formation when the universe was a few billion years old.
Now, a group of astronomers led by Manisha Caleb of the University of Sydney in Australia, reports the detection of such a high-redshift FRB. They identified FRB 20240304B at a redshift of approximately 2.148, which corresponds to just 3 billion years after the Big Bang.
"Our discovery of FRB 20240304B at zspec = 2.148 ± 0.001 during the peak of galaxy formation approximately 10 billion years ago underscores the potential of FRBs as powerful probes of the cosmic web," the researchers wrote in the paper.
FRB 20240304B was identified on March 4, 2024 by the Transient User Supplied Equipment (TUSE) instrument of the MeerKAT telescope. The burst was detected with an observed dispersion measure of 2,458.20 pc/cm3, had a peak flux of 0.49 Jy and a scattering time of 5.6 milliseconds at 1.0 GHz.
Caleb's team localized FRB 20240304B to a low-mass, clumpy, star-forming host galaxy using the James Webb Space Telescope (JWST). The host has a stellar mass of some 10 million solar masses, a star-formation rate of 0.2 solar masses per year, and a gas-phase metallicity of about 10–20% the solar metallicity.
All in all, the results confirm that FRB 20240304B is the most distant FRB discovered to date and the first to be detected at cosmic noon—a period in the universe's history (about 10–11 billion years ago) when star formation rates were at their highest. The discovery of this burst doubles the redshift reach of localized FRBs.
The astronomers noted that FRB 20240304B is highly linearly polarized with a linear polarization fraction of 49% and a negligible circular polarization fraction of 3%. They added that the magnetic fields along the line-of-sight of this FRB are either weaker than expected or most likely more complex.
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More information: Manisha Caleb et al, A fast radio burst from the first 3 billion years of the Universe, arXiv (2025).
Journal information: arXiv
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