Powerful radio signal has just reached Earth after traveling 10 billion years through space
A radio flash from the distant universe arrived after about 10 billion years in flight. Astronomers call it FRB 20240304B, a fast radio burst (FRB) that lasted only a few thousandths of a second.
These bursts are brief, bright, and packed with clues about the gas and magnetic fields between their source and Earth. They matter because each one carries a fingerprint of the matter it passed through.
Studying FRB 20240304B
The study reports FRB 20240304B at a redshift of 2.148, which means the burst left when the universe was only about 3 billion years old.
Redshift describes how light stretches as space expands, shifting radio waves to longer wavelengths with distance, and the team presented the detection, the host galaxy, and the physical inferences in their paper.
Manisha Caleb of the University of Sydney led the international collaboration that used the MeerKAT radio telescope in South Africa.
Her team localized the burst and then used the James Webb Space Telescope (JWST) to confirm the host galaxy.
FRBs show a frequency dependent delay that reveals the dispersion measure (DM) along the line of sight. That delay encodes how many free electrons the pulse encountered before it reached our instruments.
A high dispersion measure points to a long journey through diffuse ionized gas. This is why the team pursued deep imaging and spectroscopy to find a very faint, faraway host.
How the burst was caught
FRB 20240304B was found on March 4, 2024, during a targeted transient search on MeerKAT. The burst had a peak flux near 0.49 jansky and a scattering time of about 5.6 milliseconds at 1.0 gigahertz across the observed band.
The detection relied on the MeerTRAP program and its Transient User Supplied Equipment (TUSE).
That system performs real time searches on MeerKAT and enables precise follow up, and it captures triggered voltage data that make accurate positions possible.
Coherent beamforming across many dishes concentrates sensitivity and sharpens the sky position. That capability is crucial when the burst itself lasts only a blink and leaves no afterglow.
The burst was highly linearly polarized at 49 percent and showed only about 3 percent circular polarization.
Those properties help researchers probe magnetic environments near the source and along the sightline.
Why cosmic noon matters
The burst came from a time nicknamed “cosmic noon,” when the universe was forming stars at its fastest rate.
Astronomers see a peak in the cosmic star formation history about 10 to 11 billion years ago, and this event sits in that era.
Finding an FRB there matters for more than a date on a timeline. It shows that whatever powers FRBs was active when young galaxies were busy building their stars.
“This discovery doubles the redshift reach of localized FRBs. Our observations establish FRB activity during the peak of cosmic star formation” wrote Caleb.
What the host galaxy tells us
The host is a low mass, clumpy, star forming dwarf with only about ten million solar masses in stars. It forms roughly 0.2 solar masses of new stars each year and has a metallicity around 10 to 20 percent of the Sun.
Those traits point to short delays between stellar birth and FRB activity.
Young neutron stars with enormous magnetic fields, called magnetars, are a leading candidate because they can form quickly after massive stars explode.
As further evidence, a radio flash from the Galactic magnetar SGR 1935+2154 showed that magnetars can make millisecond bursts of FRB like power.
The FRB was localized with help from JWST spectroscopy that measured strong emission lines at the host position.
That enabled an accurate redshift and energy estimate for the burst without guessing the distance.
For its size, the rate of new star formation is intense compared with typical dwarfs at the same mass. That context strengthens the case that a recent massive star created a compact remnant that powers the burst.
FRBs and magnetism
The burst’s linear polarization let the team measure a rotation measure of about minus 55.6 radians per square meter.
Combined with the dispersion measure, that implies a weak average line of sight magnetic field, or a tangle of fields that cancel.
The data also show that the sightline crosses structures like the Virgo Cluster and a foreground group, which can add to the dispersion.
Accounting for those foregrounds helps isolate what belongs to the host galaxy and local environment.
Low-net Faraday rotation, despite a large dispersion measure, hints at multiple regions with opposing field directions. That pattern fits a complex medium in the host or along the path where fields reverse and partly cancel.
FRB 20240304B advances astronomy
FRBs are also tools. They turn the universe into a laboratory for counting matter and mapping magnetism.
The way dispersion grows with distance follows the Macquart relation, which links the pulse delay to the amount of plasma in intergalactic space.
That relation has already helped track the missing baryons that were hard to count in the thin intergalactic medium.
A single well measured FRB at high redshift stretches that yardstick deeper into cosmic time and puts new constraints on how much ordinary matter lies between galaxies.
This burst shows that our telescopes can reach into the early universe with enough sensitivity to localize the source.
It also shows that small, vigorously star forming galaxies can host powerful radio engines. The discovery adds a new anchor for population studies and survey design.
It raises the odds that the next generation of radio arrays will build a dense grid of sightlines that cross the cosmic web at many distances. That is how FRBs become a practical tool for mapping the matter between galaxies.
The study is published in arXiv.
Image credit: van Leeuwen/ASTRON.
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