A radio flash lasting a few milliseconds crossed more than 10 billion years of cosmic history before being detected on Earth.
The signal, named FRB 20240304B, was detected on March 4, 2024, by the MeerTRAP project using the MeerKAT radio telescope in South Africa. Fast radio bursts are extremely brief and powerful pulses whose physical origin remains uncertain.
Spectrum of the host galaxy of FRB 20240304B measured by James Webb. The oxygen and hydrogen lines confirmed a redshift of 2.148.
Credit: NASA, ESA, CSA, Joseph Olmsted; science: Manisha Caleb.
The radio signal immediately indicated that the source had to be very distant. Over such a journey, different frequencies do not pass through the ionized gas between galaxies in exactly the same way. Their delay makes it possible to estimate the amount of matter encountered, but cannot by itself determine a precise distance.
The researchers therefore searched for the source galaxy. The James Webb Space Telescope spotted a faint galaxy exactly in the region located by MeerKAT. Its infrared camera made it possible to measure a redshift of 2.148.
This value places the emission roughly three billion years after the Big Bang. The light and radio waves from the system therefore traveled for more than 10 billion years before reaching us. It is the most distant localized fast radio burst announced to date.
Deep field from James Webb showing the host galaxy of FRB 20240304B, indicated in the inset.
Credit: NASA, ESA, CSA and STScI, via HotHardware.
Its host galaxy also holds a surprise. It is relatively small and young compared with many galaxies already associated with these bursts. This shows that the phenomenon could have occurred very early after the formation of the first generations of stars in this galaxy.
Astronomers still do not know exactly which objects produce all fast radio bursts. Some recent observations link at least some of them to magnetars, neutron stars with an extreme magnetic field. Other environments could also play a role.
Such a distant event is of interest to cosmologists. During its journey, the signal passes through the very diffuse gas located between galaxies. The way its frequencies are delayed can be used to measure this nearly invisible matter and track its distribution at different periods in the Universe.
The combination of MeerKAT and James Webb therefore opens a new way to detect and analyze the most distant bursts. Future detections may show whether young, low-mass galaxies were common sites for these radio explosions when the Universe was only a few billion years old.