An international team of scientists, including at the University of Sydney, has spotted a remote blast of cosmic radio waves lasting less than a millisecond. This ‘fast radio burst’ (FRB) is the most distant ever detected.
The discovery of the burst, named FRB 20220610A, was made in June last year by CSIRO’s ASKAP radio telescope on Wajarri Yamaji Country in Western Australia and it smashed the research team’s previous distance record by 50 percent.
This FRB is also one of the most energetic ever observed; in a tiny fraction of a second it released the equivalent of our Sun’s total emission over 30 years. The location of the source is in a galaxy so far away that its light took eight billion years to reach Earth.
In a paper published today in Science, the team led by Macquarie University’s Dr Stuart Ryder and Swinburne University of Technology’s Associate Professor Ryan Shannon, report on their discovery.
Co-author Professor Elaine Sadler, from the Sydney Institute for Astronomy at the University of Sydney, said: “Tracking down the galaxy where the fast radio burst originated was very exciting, because it suggests that we will be able to find even more distant bursts in the future, allowing us to probe further into the Universe.”
Dr Ryder from Macquarie University said: “Using ASKAP’s array of dishes, we were able to determine where the burst came from.
“Then we used the European Southern Observatory’s Very Large Telescope in Chile to search for the source galaxy. We found it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies.”
Professor Sadler, also part of the School of Physics at the University of Sydney, said: “The distant galaxy where this burst originated looked quite different from the other galaxies where FRBs had been detected and we think we may be seeing the collision and merger of two galaxies rather than just a single galaxy.
“Galaxy collisions of this kind were more common in the distant and early Universe than they are today. Even though this galaxy is billions of light years away, measurements with a range of telescopes have allowed us to measure its size and mass as well as the typical age and chemical composition of its constituent stars.
“This information is helpful in trying to pin down the physical mechanism that produces such highly energetic magnetic flares, represented by the FRBs.”
The discovery confirms that FRBs can be used to measure the 'missing' matter between galaxies, providing a new way to 'weigh' the Universe.
Current methods of estimating the mass of the Universe are giving conflicting answers and challenging the standard model of cosmology.
“If we count up the amount of normal matter in the Universe – the atoms that we are all made of – we find that more than half of what should be there today is missing,” Associate Professor Shannon said. “We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it's impossible to see using normal techniques.
“Fast radio bursts allow us to detect this ionised material. Even in space that is nearly perfectly empty they can 'see' all the electrons, and that allows us to measure how much stuff is between the galaxies,” he said.
Finding distant FRBs is key to accurately measuring the Universe’s missing matter, first demonstrated by the late Australian astronomer Jean-Pierre ('J-P') Macquart in a Nature paper in 2020.
Dr Ryder said: “J-P showed that the further away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation. Some recent fast radio bursts appeared to break this relationship. Our measurements confirm the Macquart relation holds out to beyond half the known Universe.”
About 50 FRBs have been pinpointed to date – nearly half using ASKAP. The authors suggest we should be able to detect thousands of them across the sky, and at even greater distances.
Associate Professor Shannon said: “While we still don’t know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe.”
The result represents the limit of what is achievable with telescopes today, although astronomers will soon have the tools to detect even older and more distant bursts, pin down their source galaxies and measure the Universe’s missing matter.
The international SKA Observatory is currently building two radio telescopes in South Africa and Australia that will be capable of finding thousands of FRBs, including very distant ones that cannot be detected with current facilities.
ESO’s Extremely Large Telescope, a 39-metre telescope under construction in the Chilean Atacama Desert, will be one of the few telescopes able to study the source galaxies of bursts even further away than FRB 20220610A.
Ryder, et al. ‘A luminous fast radio burst that probes the Universe at redshift 1’, Science (October 2023) DOI: 10.1126/science.adf.2678
Funding for this research came from the Dutch Research Council, the Australian Research Council and the US National Science Foundation.