Granitelike LIGO saw first merger «normal» black holes

© Photo : Michael Koppitz / aetac the artist imagined merging black holes and they produce gravitational wavesGranitelike LIGO saw first merger «normal» black holes© Photo : Michael Koppitz / aei

. The gravitational wave detectors LIGO caught the first burst of fluctuations in the fabric of space-time generated by the fusion of «normal», relatively small black holes, according to a paper aimed for publication in the Astrophysical Journal Letters.

«This system is currently the easiest of the ones that we have found in the framework of Advanced LIGO. One of the black holes is 12 times heavier than the Sun and the other about 7 times, and both these masses are well within the values that were obtained in observations of double stars rengenovskim that for the first time allows us to compare the data from LIGO observations in the electromagnetic spectrum,» said the scientists.

The gravitational wave detector LIGO has been built in 2002 on projects and plans that have been developed by a Kip Thorne, Rainer Weiss and Ronald Drever in the late 80’s of the last century. In the first stage of its work, which lasted 8 years, LIGO has failed to detect the «Einstein» fluctuations in space-time, after which the detector was disabled and the next 4 years, scientists have spent on upgrading it and increasing sensitivity.

These efforts were justified – in September 2015, in fact, immediately after switching on the upgraded LIGO, scientists detected a burst of gravitational waves generated by merging black holes with total mass in 53 of the Sun. In 2016, the Russian and foreign participants of the project has opened two tracks merging black holes, and this year two other similar events and outburst, born of the merger of neutron stars.

All five of gravitational wave bursts, LIGO open, have one interesting feature – they were all generated by objects whose weight is 2-3 times higher than among black holes, opened in a double or triple star systems in the milky Way and nearby galaxies. Scientists do not yet know how to form such a heavy black hole, and whether they, in principle, result from the gravitational collapse of very large stars.

As noted by the participants in LIGO, all the doubts that «normal» black holes of smaller masses, too, can participate in such events, vanished in the early morning of June 8 this year, when both detector Observatory recorded the vibrations generated by merging pairs of black holes, distant from the Earth approximately 1.1 billion light-years.

The signal from this event was unusually powerful, well noticeable to the eye even without cleaning data from the noise that actually saved this discovery from oblivion – at the same time, the team conducted a calibration of the LIGO mirrors to the detector in Hanford, trying to increase its sensitivity, and automatic system of signal registration was not working.

In addition, high power signal allowed scientists not only to accurately calculate the masses and other properties of black holes, but also to narrow the area in which they presumably are, to a very narrow strip in the sky even without the help of the European VIRGO detector, which was incorporated only a month after this event. As physicists say, it is on the Northern half of the celestial sphere and occupies an area equivalent to about two small constellations.

The opening of such a small black holes, as noted by the team LIGO, will be especially interesting for astrophysicists, because now they have the opportunity to study the properties of «ordinary» black holes, dozens of which were opened in recent years in the so-called x-ray binary stars.

For example, the observation of this event, named GW170608, suggests that black holes in these systems have near-zero speed of rotation around its axis. This casts doubt on a number of theories describing how born such a pair of former stars.

At the end of August this year, LIGO has ceased operations and went into the next «vacation», after which the end of 2018, the sensitivity of detectors will increase to such a level that, as physicists hope they will find these events almost every week. Their study will help to understand as there are pairs of black holes and their merger affect the lives of galaxies and clusters of stars.

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