NASA’s Oct. 8 account identifies FRB 20240304B as the most distant fast radio burst seen to date. The host galaxy’s redshift—the shift of its light toward longer wavelengths—is 2.148 ± 0.0013, a measurement that places it about 3 billion years after the Big Bang, according to the study published in Science.
How astronomers measured the host’s redshift
A fast radio burst, or FRB, is a brief, intense pulse of radio waves from space. The MeerTRAP team detected FRB 20240304B with South Africa’s MeerKAT radio telescope on March 4, 2024. NASA says the James Webb Space Telescope then helped pin down its home: NIRCam identified the host galaxy, and NIRSpec measured the galaxy’s redshift.
Those are distinct steps. MeerKAT detected the burst; Webb’s instruments connected it to a galaxy and measured that galaxy’s redshift. The measurement places the host in an era about 3 billion years after the Big Bang, when cosmic star formation was near its peak.
Why the host and signal matter
The host is a low-mass, clumpy galaxy that is actively forming stars. NASA reports that it was about 1,000 times less massive than astronomers expected. The galaxy’s rate of star formation also suggests that most of its stars may have formed within about 30 million years.
The burst offers more than a way to locate its host. Its signal probes ionized gas across roughly 80% of cosmic history. NASA also reports signatures in the signal from a previously unknown galaxy cluster at redshift 0.3 and from the Virgo Cluster, about 54 million light-years from Earth.
The burst’s strongly scattered emission has another implication: the Science study says it suggests current surveys miss a population of FRBs. If so, the bursts astronomers detect may represent only part of the population, and signals such as this one can help reveal what lies between galaxies.
What the evidence says about the burst’s origin
The host’s active star formation fits one possible explanation: a young magnetar, a highly magnetic neutron star, could produce an FRB relatively soon after a massive star’s supernova. A neutron-star merger, by contrast, can follow a long inspiral that may take billions of years.
Lead author Manisha Caleb said a merger is very unlikely for FRB 20240304B. A young magnetar remains a possible explanation, but the burst’s source mechanism has not been established; FRB origins remain unexplained.
