New observations of mysterious FRB outbreaks indicated that all such events must be generated by their sources several times during their entire existence. This excludes the possibility that they could be generated by exploding stars and merging black holes, writes the astronomer in the journal Nature.
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 with the Parks telescope (Australia).
In subsequent years, scientists managed to find traces of another three dozen 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.
All of them were united by one thing - an extremely high power and an unusually long distance to their sources. Therefore, initially, astronomers assumed that such bursts are born during the merger of neutron stars or other compact objects that turn into a black hole.
Two years ago, scientists found hints that this was not the case. The Parks Telescope recorded repeated flares at the point where one of the first FRB bursts was recorded six years ago, the FRB 121102 event. This made the "alien signals" even more mysterious and interesting space phenomena.
Subsequently, astronomers were able to localize the source of this outbreak - an invisible dwarf galaxy in the constellation Auriga, three billion light-years away from us. At the same time, the exact position and nature of not a single single burst was never found out, which made the researchers fiercely argue about whether they differ from FRB 121102.
Ravi suggests that the sources of the lone alien radio signals are no different in nature from FRB 121102 and another recurring outbreak, FRB 180814, after analyzing the latest data collected by two relatively new radio telescopes, Canada's CHIME Observatory and its Australian cousin ASKAP.
Both of these installations can track fairly wide sectors of the night sky, which allowed them to record several dozen FRB bursts during the first months of their operation. This more than doubled their total number and made scientists wonder how often we should hear the "call" of aliens.
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The fact is that the frequency of these events varied sharply, according to the data from CHIME and ASKAP. The Canadian observatory found about ten times more flares than its Australian rival, which made scientists doubt that all observations of FRB flares were true.
These discrepancies, as Ravi's calculations showed, were not due to errors of astronomers or problems in the operation of instruments, but to the fact that ASKAP is simply rather poor at picking up "alien signals" that arose at a sufficiently large distance from the Milky Way. This discovery helped him combine their observations and accurately calculate the frequency of occurrence of FRB bursts in the night sky.
As it turned out, these outbursts occur unexpectedly often, and even in the most extreme cases, their frequency is more than how often neutron stars, pairs of white dwarfs merge, rare and "ordinary" supernovae explode, and all other cataclysms occur.
All of this, according to Ravi, suggests that almost all or most of FRB flares are generated by sources that can emit not one, but a large number of such flares. Their total number may be small enough, about 100 events during the entire existence of the Universe, to explain the frequency of flares, which was recorded by the CHIME telescope.
This, however, poses a new question for scientists: why such properties were discovered only in two out of seven dozen known "signals from aliens". The answer to it, as suggested by the Harvard astrophysicist, can be obtained by understanding in which parts of galaxies FRB bursts are born.
So far, such information is known only for FRB 121102 and one "single" outbreak discovered in September last year, which does not allow any conclusions about their nature to be drawn.
