The LIGO and VIRGO gravitational observatories for the first time simultaneously detected a burst of gravitational waves generated by the merger of two black holes and localized their source - one of the galaxies in the constellation of the Hours, said participants in the VIRGO and LIGO collaborations, speaking at a press briefing at the meeting of the G7 ministers in Italian Turin.
“The combination of LIGO and VIRGO not only increased the localization accuracy of gravitational wave sources by 20 times, but also allowed us to start searching for traces of objects generating gravitational waves in other types of radiation. Today we have truly entered the era of full-fledged gravitational astronomy,”said David Shoemaker, head of the LIGO collaboration.
Looking for folds of space-time
The LIGO gravitational wave detector was built in 2002 according to projects and plans that were developed by Kip Thorn, Rainer Weiss and Ronald Drever in the late 1980s. At the first stage of its work, which lasted 8 years, LIGO was unable to detect the "Einstein" oscillations of space-time, after which the detector was turned off and the next 4 years scientists spent on updating and increasing the sensitivity.
These efforts paid off - in September 2015, almost immediately after the inclusion of the updated LIGO, scientists discovered a burst of gravitational waves generated by merging black holes with a total mass of 53 Suns. Subsequently, LIGO recorded three more bursts of gravitational waves, only one of which was officially recognized by the scientific community.
Scientists do not know exactly where the sources of these gravitational waves were located - due to the fact that LIGO has only two detectors, they only managed to identify a fairly narrow strip in the night sky where these black holes could be. Inside it, despite its modest size, there are millions of galaxies, which makes the search for the “end product” of these mergers virtually useless.
In June this year, the European "cousin" of LIGO, the VIRGO gravitational observatory, built in the vicinity of Pisa, Italy in 2003, resumed its work. The operation of VIRGO was suspended in 2011, after which the observatory's engineering team carried out a deep modernization, bringing it closer in sensitivity to the current level of LIGO.
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All inspections of the VIRGO detectors were completed by 1 August this year, and now the observatory has begun joint observations with two LIGO detectors. Its sensitivity is slightly lower than that of the American gravitational telescope, but the data it receives allows it to solve two major scientific problems - to improve the quality and reliability of the signal received by LIGO, and to determine the "three-dimensional" position of the source of gravitational waves.
Einstein Triangulation
Scientists have achieved the first results unexpectedly quickly - already on August 14 they managed to detect the burst GW170814, which originated in a distant galaxy at a distance of 1.8 billion light years from Earth. As in the previous three cases, these waves were generated by unusually large black holes, whose masses were 30.5 and 25 times greater than the sun. During their merger, approximately three solar masses "evaporated" and were spent on the emission of gravitational waves.
The use of three detectors at once allowed scientists to significantly increase the accuracy of localizing the source of gravitational waves - the galaxy in which the black holes that generated them are located is located in a small area of the sky in the constellation of Hours in the night sky of the southern hemisphere of the Earth. In addition, scientists plan to use this data to search for possible traces of this outbreak in the radio and X-ray ranges.
One of the peculiarities of the European detector, as added by Jo van den Brand, head of the VIRGO collaboration, is that it is turned slightly in the opposite direction compared to a couple of its American counterparts. This allows scientists to use them to measure the polarization of gravitational waves and test some of the main provisions of the theory of relativity, as well as search for parallel worlds.
There was no sensation in this case - a preliminary analysis of the data collected by LIGO and VIRGO during this outbreak shows that gravitational waves travel through space and behave exactly as predicted by Einstein's theory. In the future, when the sensitivity of LIGO and VIRGO is increased, scientists hope to find a definitive answer to this question.
Shoemaker noted that the LIGO detectors were turned off on August 25 in order to approximately double their accuracy. This "upgrade", he said, will expand the "horizon" of the observatory by about nine times, and will allow traces of merging black holes to be found almost every week.
