Astronomers have detected the most distant burst of radio signals ever seen: an explosion that’s emitting waves of energy from more than 10 billion light-years away.
The event, named FRB 20240304B, is known as a fast radio burst (FRB). Astronomers have detected thousands of FRBs before this. But because these events last only milliseconds, they are extremely difficult to study and their origin stories remain unclear.
In this case, however, astronomers managed to use a radio telescope array and the James Webb Space Telescope (JWST) to chart the event, with JWST narrowing down the precise host galaxy that FRB 20240304B came from. The study, published Thursday (Oct. 8) in the journal Science , sheds more light on a time when the universe was only about 3 billion years old, showing that FRBs arose early in our cosmos’ history. The detection more than doubles the previous distance record for FRBs.
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The JWST played an instrumental role in the discovery, study co-author Themiya Nanayakkara, a senior lecturer at the Sydney Institute for Astronomy, told Live Science in an email. The email was written in collaboration with study first author Manisha Caleb, a senior lecturer in astrophysics at the same university.
For example, JWST’s observations showed that the host galaxy was smaller than expected, was “metal-poor” (had few elements besides hydrogen and helium), and was forming a lot of stars. These characteristics could offer new clues about the environments in which FRBs arise, giving more information about the mysterious events. Researchers suggest that this FRB may have been linked to a magnetar, a highly magnetic star core left after a supernova.
Zooming in with the James Webb telescope
The ancient FRB was initially detected with MeerKAT, an array of 64 radio telescopes in South Africa. Nanayakkara said MeerKAT revealed “both the detection of the fast radio burst and, importantly, a very precise position on the sky.”
The researchers knew the FRB was far away because of the large dispersion of the radio signal, but initial searches with powerful ground-based telescopes, “saw essentially nothing; it looked like empty sky,” the researchers told Live Science. “The most likely explanation was that the galaxy was simply too faint to be detected in those observations. That is where JWST became transformative.”
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An illustration of a fast radio burst (FRB) being detected by the MeerKAT radio telescope array.
(Image credit: Carl Knox – OzGrav, Swinburne University of Technology Background Image Credit: NASA, ESA, CSA, STScI, Themiya Nanayakkara (USYD) Background Image Processing Credit: Joseph DePasquale (STScI))
The science team successfully got time on JWST with a program called Director’s Discretionary Time, which is aimed at time-sensitive observations. The researchers started by using JWST’s Near Infrared Camera to trace the radio signal and take a very deep image of the target region.
“Suddenly, there it was: a very faint galaxy almost exactly where we expected the host of the FRB to be,” Nanayakkara said. The researchers then used JWST’s Near Infrared Spectrograph to obtain a spectrum (wavelengths of light broken into different chemical signatures), which showed hydrogen and oxygen.
“These spectral features act like fingerprints: because we know the wavelengths at which they are produced in the laboratory, we can measure how much they have been shifted by the expansion of the universe,” Nanayakkara explained. “That gave us a very precise redshift of about 2.15. We are therefore seeing this galaxy as it was when the universe was only around three billion years old, so roughly one-fifth of its current age.”
Because the host galaxy is fairly young, it supports the idea that at least some FRBs are generated by magnetars, which are more likely to appear in spry galaxies where intense star formation is occurring, the team said.
The team plans to continue hunting for FRBs with JWST.
“We do not know what the sources will be yet,” Nanayakkara said, as that depends on what pops up in the sky and is spotted by ground-based radio telescopes. “Once our radio telescopes find and localize a suitable new source, we can trigger the JWST observations. So it is quite exciting, because we really have no idea what we will find when we combine the power of these two types of telescopes.”
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