Mysterious ultrafast radio flares, the nature of which remains a mystery to astronomers, originate outside the Earth and, probably, our entire Galaxy as a whole, according to an article accepted for publication in the journal MNRAS.
“Perhaps the strangest explanation for these outbreaks is that they are signals from aliens. Understanding where these flashes come from is the key to uncovering the object that gives rise to them. So far, only one particular burst has been associated with a distant galaxy. We expect our Molonglo interferometer to help find sources for other flares,”says Manisha Caleb of the National University of Australia in Canberra.
Are we alone in the universe?
For the first time, astronomers started talking about the existence of mysterious bursts of radio emission (fast radio-burst, FRB) in 2007, when they were accidentally discovered during observations of radio pulsars using the Parks telescope (Australia).
In subsequent years, scientists managed to find traces of nine more such bursts, a comparison of which showed that they can be of artificial origin and even potentially be signals of extraterrestrial civilizations due to the inexplicable periodicity in their structure.
Last spring, scientists discovered that the source of one of these FRB flares was an elliptical galaxy located 6 billion light-years from the Milky Way, leading them to conclude that such bursts are born during the merger of neutron stars or other compact objects that turn into black hole.
According to Caleb, this discovery did not convince many scientists of the "extraterrestrial" origin of the flares, since only one of them was located with a sufficiently high accuracy. In addition, very similar to FRB-signals, the so-called peritons, were not generated by "aliens" or objects in space, but by microwaves at the Australian Parks Observatory, where they were discovered about ten years ago.
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Caleb and her colleagues confirmed that FRB flares actually originate in deep space, not on Earth, by capturing several new signals of this type and studying their spectrum with the Molonglo radio telescope-interferometer in southern Australia. Interferometers, as the scientists explain, are special "virtual" radio dishes of enormous size, which astronomers "collect" by combining the signal from several separate radio telescopes in different parts of the Earth or even space.
According to Caleb, this discovery did not convince many scientists of the "extraterrestrial" origin of the flares, since only one of them was located with a sufficiently high accuracy. In addition, very similar to FRB-signals, the so-called peritons, were not generated by "aliens" or objects in space, but by microwaves at the Australian Parks Observatory, where they were discovered about ten years ago.
Caleb and her colleagues confirmed that FRB flares actually originate in deep space, not on Earth, by capturing several new signals of this type and studying their spectrum with the Molonglo radio telescope-interferometer in southern Australia. Interferometers, as the scientists explain, are special "virtual" radio dishes of enormous size, which astronomers "collect" by combining the signal from several separate radio telescopes in different parts of the Earth or even space.
Dark radio skies
Using the interferometer, the scientists hoped not only to prove that FRB signals were not generated inside the observatories themselves that had detected them in the past, but also to find its source using the giant sensitivity and size of Molonglo's "virtual dish". The idea was quite simple - if FRB flares were born on Earth, then the interferometer would not see them, since it can record radio signals that are born at an altitude of at least a thousand kilometers from the planet's surface.
In total, Caleb and her colleagues were able to record the birth of three radio flares, and measure their spectrum quite accurately and determine that they all originated in outer space, and not on Earth - in the constellations Hydra, Carina and Stern.
None of these flares were repeated, which did not allow scientists to determine exactly in which galaxy they originated, but at the same time they were able to calculate how many of these "alien signals" should hit the Earth every day - about 78 FRB bursts.
This discovery came as a big surprise to astronomers, since the frequency of such flares recorded by the Parks telescope was about 100 times lower. Why this is so, scientists do not know, but they assume that it is due to extremely distant sources for most FRB flares, which the Parks telescope simply cannot see due to lower sensitivity.
What is causing these mysterious outbursts? The answer to this question has not become clearer, but Caleb's team suggests that the data they obtained provide more evidence that the sources of these flares are pulsars, and not merging black holes or gamma-ray bursts, as other scientists believe. In any case, as astrophysicists admit, we will get an exact answer to this question only when the sources for at least several FRB flares are localized, which takes a lot of time.
