An 8 billion year journey to a radio telescope antenna, or a bit about the oldest fast radio burst

In June 2022, astronomers detected an unusual burst of radio waves that traveled through the universe for about 8 billion years, roughly half the age of the universe, before reaching telescopes on the earth. This explosion, known as FRB 20220610A, was one of the most distant and powerful ever observed. It also challenges existing models about the origin and nature of these mysterious signals.

Fast radio bursts, or FRBs, are millisecond-long bursts of intense radio waves from an unknown source. Since their discovery in 2007, hundreds of these explosions have been recorded on Earth, but most are not repeated and their exact location in the sky is difficult to determine. They are thought to come from highly magnetic neutron stars in distant galaxies, but the exact mechanism by which they are created remains a mystery. FRB 20220610A was discovered by the Australian Kilometer Array Pathfinder (ASKAP) radio telescope and is the oldest FRB ever measured. To identify the burst’s source galaxy, scientists also used the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile and the West. M. Keck Observatory in Hawaii.

The age of the FRB was the biggest surprise for the researchers, who published their results in the journal Science. “We don’t know whether fast radio bursts last that long,” said Stuart Ryder, study co-author and astronomer at Macquarie University in Sydney, Australia. Ryder said FRBs are useful astronomical tools for analyzing the universe because they allow scientists to detect and measure intergalactic matter that we currently cannot see. As FRBs move through and between galaxies, they pass through hot gas, slowing down lower frequency radio waves more than higher frequencies. This phenomenon is called dispersion. This means that radio waves of different frequencies reach telescopes on Earth with a small time difference, allowing scientists to infer the presence of material that the FRB passes through.

The signal produced by the new FRB is more scattered than most previous observations, suggesting that FRB 20220610A has had a bumpy ride in its 8 billion year journey. The unusually widespread signal, along with its enormous distance from its source galaxy, also confirms what previous studies of nearby FRBs suggested: the farther away they are, the more their signal is distorted. dispersed upon reaching Earth.

The FRB also has high power, emitting 3.5 times more energy than the maximum predicted by the simulation. Ryder said such calculations need to be adjusted to account for these extreme events. “We can now refine our estimate of the energy distribution of the explosions,” he said. Kiyoshi Masui, an astrophysicist at the Massachusetts Institute of Technology in Cambridge, US, is not surprised that FRBs exist at such distances. Scientists can learn a lot from these distant pulses, he said. He added that to better understand the nature of FRBs, it is necessary to detect more signals of this type and determine their exact coordinates.

Currently, several FRB research projects are in development or underway. One of these is the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which uses an array of four hemispherical antennas to detect FRBs over a wide frequency range.