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Four radio telescopes collected many bright fast radio bursts from one repeating source – many more than expected. Illustration: Daniëlle Futselaar/artsource.nl

Fast radio bursts have mystified astronomers for over fifteen years. Often lasting only milliseconds, these brief, bright flashes of radio waves can be detected from far out in the universe by radio telescopes.

In a new study, scientists used radio telescopes in Sweden, Germany, the Netherlands, and Poland to monitor a repeating source of fast radio bursts. “This is the longest study yet of a single source of fast radio bursts,” says Wolfgang Herrmann, amateur radio astronomer and member of the science team.

46 bright bursts
Over several weeks, the four telescopes stared at the radio source for up to 12 hours per day. The observing campaign was shared between four telescopes, the 25-metre diameter telescope in Onsala, Sweden, one 25-metre dish of the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands, the 32-metre telescope in Toruń, Poland, and the 25-metre telescope in Stockert, Germany. The Stockert telescope is run by the non-profit organisation Astropeiler Stockert e.V., whose members are represented in the science team.

In total, the telescopes recorded 46 bright bursts, each lasting only a few milliseconds.

“This source had been previously studied with a much bigger radio telescope, FAST in China, so we knew what to expect. But we were really surprised by what we saw. Of the bursts that we collected, far more than we expected of them were very bright ones,” explains Franz Kirsten, astronomer at Onsala Space Observatory, Chalmers.

Surprising conclusions
If this repeating source is typical, the astronomers reason, then they can draw two surprising conclusions.

First, the new observations point to a surprising new interpretation about the sources of fast radio bursts. Of the bursts that have been recorded so far, almost all have only ever been seen once. “Since some sources repeat, it has been speculated that all of them could. Now finally, we have statistics on a repeater that allows us to make a proper comparison to non-repeaters. And it looks like that could really be true: all fast radio bursts will repeat if you look long enough,” says team member Omar Ould-Boukattine, astronomer at ASTRON and the University of Amsterdam.

Secondly: the brightest fast radio bursts could be seen at vast distances. “We think bright bursts like these could be seen from the most distant galaxies known, like those discovered recently by the James Webb Space Telescope, which we see in light that has travelled to us since the universe was only a few hundred million years old,” says Marcin Gawroński, team member at the Nicolaus Copernicus University in Toruń, Poland.

History of the universe
Though scientists don’t yet know what causes fast radio bursts, there are many signs that connect them to dense, magnetised remnants of exploded stars called magnetars and neutron stars.

“If we can see fast radio bursts from the time when the very first stars and galaxies were shining, that would give us a completely new way of accessing that time in the universe’s history,” says Franz Kirsten.

The research results are published in paper, A link between repeating and non-repeating fast radio bursts through their energy distributions, published on 4 January 2024 in the journal Nature Astronomy.

ASTRON