2023-10-19 18:38:37
Space
A “radio burst” from a very distant galaxy
An explosion of radio waves was captured by an Australian telescope in June 2022.
PublishedOctober 19, 2023, 8:38 p.m.
Hundreds of thousands of fast radio bursts may occur in the sky every day.
AFP/Photo d’illustration
It took eight billion years to reach us: astronomers detected an incredibly powerful explosion of radio waves in a very distant galaxy. A discovery which should help elucidate the mystery of this cosmic phenomenon, according to a study published Thursday.
This “fast radio burst” called FRB (Fast Radio Burst), a flash of electromagnetic waves lasting less than a thousandth of a second, finally reached Earth on June 10, 2022, where an Australian telescope managed to pick up its signal.
It came from a much more distant galaxy than previously recorded FRBs, having traveled eight billion light years, a time when the Universe was less than half its current age, astronomers reveal in the magazine «Science».
Dead star
Since the first detection of such signals in 2007, scientists have wondered about the exact origin of the cosmic phenomenon, which is all the more difficult to determine because it is stealthy.
Because these signals sometimes repeat themselves, some initially assumed that we were dealing with radio communications transmitted through space by some sort of extraterrestrial. More seriously, scientists believe the main suspect is an incredibly dense dead star called a magnetar, with an ultra-strong magnetic field.
“It’s mind-blowing” that the ASKAP telescope, located in western Australia, managed to spot this FRB, Ryan Shannon of the Australian Swinburne University (in Melbourne), co-author of the paper, told AFP. the study. “We were lucky to be able to observe this little dot in the sky for a millisecond, after the eight billion years that the pulse traveled to be captured,” adds this astrophysicist.
The radio burst easily beat the previous record, which traveled about five billion light years. With incredible power, because in less than a millisecond, the pulse released as much energy as the Sun emits in 30 years.
“Cosmic web”
Hundreds of thousands of fast radio bursts may occur in the sky every day, according to the scientist. But only a thousand have been detected so far, and researchers have only been able to determine their galaxy of origin for around fifty of them. However, this is a key element for understanding the phenomenon.
To determine the source of this distant radio burst, called FRB 20220610A, researchers turned to the Very Large Telescope (VLT) in Chile. The latter revealed that the signal came from a particularly dense galaxy which could have merged with one or two other galaxies, which would have given rise to the strange magnetar.
But this is only the “best intuition” of scientists, emphasizes Ryan Shannon. Given that the radio bursts have been detected in unexpected places, including inside the Milky Way, “the jury is still out” on what causes them, he notes.
Another mystery
In the meantime, these radio bursts could help elucidate another mystery, that of the quantity of solid matter in the Universe. It is supposed to account for about 5% of this Universe, the rest being made up of dark matter and dark energy.
The problem? More than half of this 5% of solid matter is missing. Scientists believe it lies in the cosmic web, thin filaments of gas connecting galaxies together, but so diffuse that they are invisible to telescopes.
Unless you use FRBs, which “bear the imprint of all the gas they have passed through,” explains the astrophysicist. This gas actually alters the wavelength of the FRB and thus makes it possible to measure the density of the latter.
The FRB recorded by the Australian telescope bears the imprint of “excess material”, according to the researcher. A large number of these radio waves still need to be recorded to refine the calculations of missing matter.
(AFP)Show comments
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