Abstract:
An international team led by the University of Sydney in Australia used the MeerKAT radio telescope in South Africa and the James Webb Space Telescope to capture and locate the most distant fast radio burst to date, FRB 20240304B. Its source is located in a galaxy about 3 billion years after the Big Bang. The signal traveled in the universe for more than 10 billion years, more than twice the distance of the previous FRB record. The relevant results were published in the latest issue of Science.
Artist illustration of FRB 20240304B detection. Source: "Science"
Fast radio bursts (FRBs) have puzzled astronomers since they were first discovered. This phenomenon is a radio pulse that lasts a few milliseconds and originates from outside the Milky Way. Its physical origin is mysterious, but its energy is extremely high. Despite many efforts and scientists developing relevant theories, the origin of FRBs has not yet been completely clarified. At present, magnetars are candidates for some sources; some astronomers believe that they may be the noise produced when two stars collide; and some astronomers are more willing to believe that this is a message from aliens - possibly caused by the "leakage" of technology from advanced extraterrestrial civilizations.
This radio flash lasted only a few milliseconds and also released huge energy. On March 4, 2024, the MeerTRAP project used MeerKAT to capture the burst first, and astronomers then used the Webb near-infrared camera and spectrometer to find its "home". The spectrum gives a redshift of about 2.148, which corresponds to when the universe was still very young. In the past, large ground telescopes could not see this host because it was small and dim, but Webb's infrared capabilities could lock it in.
After determining the location, astronomers found that the host was not like the mature large galaxies where most FRBs are located, but a low-mass, metal-poor dwarf galaxy that was rapidly forming stars. This type of environment is young and active in star creation, which further supports the "origin of magnetars": after a massive star becomes a supernova, it leaves behind a neutron star with a strong magnetic field, which can explode in a short time. If the merger relies on old neutron stars, it usually takes a longer evolution time, which is not suitable for this small galaxy. Based on this, the team believes that at least some of the distant FRBs may come from young magnetars.
The key point in this result is that the radio signal will "interact" with the ionized gas along the way as it "rushes". There is a slight time difference between different frequencies reaching the earth, which can be used to infer the matter hidden in the middle. There is a large amount of thin gas and cosmic web structures between galaxies, which are almost invisible at ordinary times, but the FRB illuminates the entire line of sight like a flashlight. This signal not only broke the distance record, but also provided new samples for mapping the distribution of matter, magnetic field and intergalactic medium in the early universe.
The research team stated that the next step will be to use a more sensitive radio array to superimpose the infrared equipment of the Webb Telescope to continue to look for signals earlier in the universe and closer to the first-generation stars.
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