Sergey Trushkin, an astronomer from the Special Astrophysical Observatory of the Russian Academy of Sciences, spoke about why scientists became interested in mysterious fast radio flares, the so-called radio signals from aliens, and explained how the Russian telescope RATAN-600 got a unique chance to reveal their essence.
“Given our modest capabilities, we expect that it will be possible to record at best three to five such flares per year of observations. On the other hand, even if we can find at least one event at the frequencies where the search is being conducted, this will radically change the understanding of the nature of these signals,”Trushkin said, speaking at the annual conference“High Energy Astrophysics”at the IKI RAS in Moscow.
Call of the cosmos
For the first time, astronomers started talking about the existence of mysterious bursts of radio emission (fast radio-burst, FRB), accidentally discovered during observations of radio pulsars using the Parks telescope (Australia), in 2007.
“Why didn't we find these phenomena 50 years ago, when the first radio telescopes appeared? The problem was that our predecessors did not have the high quality radio equipment that exists today. They were discovered with the help of Parks only after the update of his detectors, which allowed the discoverers to understand that these signals are not interference, born on Earth, but flashes from distant galaxies,”the scientist notes.
In subsequent years, traces of nine more similar bursts were found. The comparison showed that they can be of artificial origin and even potentially be signals of extraterrestrial civilizations due to the inexplicable periodicity in the structure.
Last spring, it was revealed that the source of one of these FRB flares was an elliptical galaxy located six billion light years from the Milky Way, and this led scientists to conclude that such bursts are born during the merger of neutron stars or other compact objects that turn into black hole.
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This theory suffered a crushing defeat in March 2016. Using the same Parks, Canadian researchers found that one of the very first flares found - the FRB 121102 burst - re-emerged at the same point in the constellation Auriga, where it was found six years ago.
According to Trushkin, this immediately cut off most of the theories in which various cosmic cataclysms acted as the progenitor of FRB flares - the formation or merging of black holes, pulsars and other compact objects that can occur only once.
The unusual properties of these radio bursts, which do not allow them to be associated with either supernova explosions or mergers of black holes or pulsars, made scientists think about more exotic variants of the birth of such "alien signals". For example, some astrophysicists believe that they can be generated by decays of axions, ultra-light particles of dark matter, exotic cosmic "strings", as well as explosions of microscopic black holes.
Last summer, Russia joined these observations, which has one of the most famous and oldest Russian telescopes, RATAN-600. It is located at the Special Astrophysical Observatory of the Russian Academy of Sciences in the village of Zelenchukskaya. The unique properties of the telescope, Trushkin and his associates hope, will help to clarify the nature of these signals and finally prove, for example, that they cannot be produced by "ordinary" pulsars.
“Now the number of theories explaining such bursts significantly exceeds the number of these phenomena known to science. We - observers and experimenters - are more interested in discovering events and obtaining new data that our theoretical colleagues can use in order to create their theories,”continues Trushkin.
Two key features of "alien radio signals", as the scientist notes, - their high brightness and extremely low duration - make it possible to bypass the main drawback of RATAN-600 - the inability to track one point in the sky for any length of time.
While observing FRB, the Russian telescope will scan the entire night sky, tracking each segment for a very short time. This will allow, despite the modest angle of view of RATAN, to cover a sufficiently large area of the sky, which will be only four times smaller than that for the Parks telescope.
“We thought for a long time what frequency to choose for these observations, and settled on a value of 4.7 gigahertz. All other bursts were detected at frequencies of 1.4 gigahertz or less, but such observations require rather expensive installations, for which we simply do not have the money. High frequencies, in turn, allow us to reduce the number of channels required for observing, and allow us to enter the area where no one has observed FRB before,”continues Trushkin.
The last car of the space train
According to him, these observations are actually a "hobby" for the observatory staff - they will be conducted in the western sector of the RATAN-600 ring, previously mothballed, as well as with the help of four backup detectors, filter sets and other radio equipment, which was purchased in the pre-crisis years and not used.
“We conducted preliminary negotiations with the Yuri Milner Foundation, which supports such initiatives, but they did not end with anything significant. On the other hand, we need a little money, about 30 thousand dollars, to double the number of detectors and significantly increase the likelihood of detecting new flares,”the scientist noted.
As the astronomer notes, Russian scientists will focus their efforts on observing the part of the sky where FRB 121102 is located. The repetitive nature of the flares, Trushkin and his associates hope, will increase the chances of RATAN-600 to detect at least one such phenomenon and allow it to be studied at lengths waves inaccessible to other radio telescopes.
Scientists have already tested the work of the updated RATAN-600 on two objects - on one of the brightest pulsars located in our Galaxy, and also by trying to detect FRB 121102. According to Trushkin, in August of this year, his team "caught" a signal coming from the same points as this re-burst.
The RATAN-600 radio telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences.
So far, there is no certainty that it was possible to record an FRB flash, since at that time the telescope was not yet fully tuned. Therefore, astronomers were unable to determine the distance to the "alien signal" and calculate its exact coordinates.
On the other hand, two other radio observatories - GBT telescopes in the United States and WSRT in Holland - recorded a repeated burst of FRB 121102 at about the same time, which confirms the hypothesis of Russian scientists.
“These observations from colleagues and our preliminary data suggest that FRB 121102 is more than just a variable and repetitive source. It can emit such impulses in peculiar bursts. In other words, it is capable of generating several outbreaks in one month, and then “silenced” for a week, a month or a conditional thousand days,”says Trushkin.
According to him, the main problem for RATAN-600 today is time. So far, only a Russian telescope can conduct such observations, but the same frequencies will become available for the SKA mega telescope, the construction of which will begin in South Africa next year.
“SKA and the Canadian project CHIME are expected to find dozens of similar outbreaks every day. While they have not yet been commissioned, we have the opportunity to make a unique contribution to the study of FRB flares due to the high frequencies at which we operate, and to somehow compete at the international level,”the astronomer concludes.