Russian and foreign astronomers working with the LIGO and ViRGO gravitational observatories have announced the discovery of four more bursts generated by black hole mergers. This was reported by the press service of Moscow State University.
“Long live gravitational wave astronomy! She was born only 3 years ago during the sensational registration of the first exotic events, she got on her feet completely and supplies more and more interesting data, without which it is already impossible to imagine the development of astronomy and cosmology, says Sergey Vyatchanin, professor at Moscow State University and one of the members collaboration LIGO.
Magnificent ten
In September 2015, virtually immediately after the updated LIGO was turned on, scientists discovered a burst of gravitational waves generated by merging black holes with a total mass of 65 Suns. Subsequently, LIGO recorded five more similar events generated, with one exception, from similar mergers of large black holes.
Their discovery launched a new series of big debates among scientists - how exactly such pairs of black holes could have arisen and whether it is possible to "see" the history of their formation in how the process of their merger takes place.
Some astronomers today believe that black holes in such pairs are born alone, and only after a very long time they meet with another similar object, approach it and merge. Such a theory imposes very strict restrictions on the frequency of such mergers and the place where they can occur - in fact, such pairs of black holes can only arise inside superdense globular clusters on the outskirts of galaxies.
It is still difficult to answer this question because of the small number of open black hole mergers. Vyatchanin and his collaborators, as well as members of the VIRGO project, almost doubled the number of known gravitational bursts, discovering many new potential bursts of "Einstein waves". This already allows some estimates to be made.
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All these events, as scientists note, were discovered during the second cycle of observations. It started in November 2016 and ended last August. In addition to the already well-known first merger of neutron stars and three echoes of a collision of black holes, scientists from LIGO and ViRGO managed to find and confirm four more events of this kind.
New secrets of space
All of them, in addition to statistics on the number of collisions of black holes, brought a lot of other discoveries. For example, the new event GW170729 was triggered by gravitational waves from the most massive and distant source ever observed.
It happened about 5 billion years ago, when two black holes merged, supposedly 50 and 35 times the mass of the Sun. According to scientists' calculations, the "product" of their merger has lost about five solar masses, whose energy was emitted in the form of gravitational waves.
The next burst, GW170809, was unique in that it was the first time scientists were able to measure the polarization of gravitational waves. This is extremely important for testing the theory of relativity and searching for possible traces of "extra" dimensions and parallel worlds.
Likewise, the third new burst of "Einstein's waves", GW170818, helped astronomers locate the source of this radiation with very high accuracy, measuring the signal delay on all three gravitational detectors to the same level.
All this, as the researchers note, allowed them to draw some conclusions about the "demography" of black holes and their potential "homeland". For example, measurements by LIGO and ViRGO have unexpectedly shown that such objects rarely have a high rotation speed. This is not typical for the known pairs of black holes and other objects in the Milky Way, and also speaks in favor of their "single birth".
On the other hand, the frequencies of mergers and typical masses of black holes still fit into the predictions of the theory. LIGO and ViRGO have not yet discovered unusually small and large objects that fall into a kind of "forbidden zone" where black holes have never been found. The LIGO update, which scientists plan to complete later this year, will help open up even more black holes and test if this trend continues in the future.
“At the beginning of next year, the third cycle of scientific observations of the LIGO and ViRGO detectors will begin. It is assumed that in this cycle they will use quantum “squeezed light” to increase the sensitivity. This will be the first use of quantum technologies in gravitational-wave detectors, which are being developed in particular by a group of Moscow University,”concludes Farit Khalili, professor at the Physics Department of Moscow State University.
