Astronomers hunting fast radio bursts have managed to locate a “unique” radio wave for the first time. Originally from a distant galaxy, it could help them map the confines of the universe.
A team of international astronomers led by Australian scientists found for the first time the precise origin of a mysterious phenomenon called “rapid radio burst” discovered in 2007. These cosmic waves can emit in a thousandth of a second the equivalent of 10,000 years of solar energy. “The whole community of astronomers was eagerly waiting for this result,” Casey Law, an astronomer at the University of California, Berkeley, told AFP. He did not participate in the published study.
This work is the most important since the discovery of these fast radio bursts (Fast Radio Burst or FRB). We do not know what produces these monstrous energy murmurs, but astronomers agree on one point: they come from galaxies very, very far away.
The hunt for these bursts has detected 85 since their identification. Most were unique: a flash and then nothing. But a few were repeated. In 2017, for the first time, astronomers have been able to pinpoint the source of a repeated burst. But locating a single burst represented another challenge.
The team, led by Australian Keith Bannister of the Commonwealth Scientific and Industrial Research Organization (CSIRO), has developed a new methodology to meet the challenge. “You can compare it to slow-motion on television: we have programmed a computer to actively search for bursts. It received a billion measurements per second and tried to find which contained an FRB,” said Banniste.
As a result, FRB 180924 was discovered by the Australian Square Kilometer Array Pathfinder (Askap radio telescope) in Western Australia. It occurred 3.6 billion light-years from Earth. The burst reached each of the 36 parabolas of this telescope at an imperceptibly different moment, which allowed the scientists to make a sort of triangulation to calculate the origin.
“It comes down to looking at the Earth from the moon and finding not only in which house a person lives, but also on which chair she is sitting in the dining room,” says Keith Bannister. Thanks to other telescopes in Chile and Hawaii, scientists were able to obtain an image of the original galaxy and its distance from the Earth. While the rapid radio burst located in 2017 came from a dwarf galaxy, the new one described in the journal Science comes from around a massive galaxy made up of ancient stars. This leads the researchers to conclude that they still do not know how these bursts are formed.
“This would imply that repeated and unrepeated rapid radio bursts have completely different origins,” said Shriharsh Tendulkar, an astronomer at McGill University, who is not a member of the research team.
Towards a map of the confines of the universe
The discovery fascinates astronomers because it provides new information about what is in the space between galaxies, and could help them solve the enigma of the “missing matter” of the universe.
Scientists have a theory to explain why the number of atoms observed in stars is less than half the theoretical calculations. Missing atoms would be found in ionized gases in intergalactic spaces. Cosmic waves disperse during their journey to the Earth: a little like light is refracted through a prism.
It turns out that the observations of the team correspond to what theory predicted on the amount of matter lying on its path. But this will have to be reinforced by thousands, even tens of thousands of additional observations, to form a map of the confines of the universe.
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