Astronomers first saw a burst of light fromcollisions of two black holes. The objects met at a distance of 7.5 billion light years from Earth. At the moment of their meeting in a whirlwind of hot matter rotating around a larger, supermassive black hole, fusion began. This whirlpool is called an accretion disk and revolves around the event horizon of a black hole - a place in space in which gravity is so strong that even photons of light cannot leave it. That is why scientists have never seen a collision of two black holes. In the absence of light, such mergers can be identified only by detecting gravitational waves - ripples in space-time created by collisions of massive objects.
Einstein was wrong?
For the first time the existence of gravitational wavespredicted Albert Einstein, but he did not think that they would ever be able to detect. They seemed too weak to catch their signal on Earth in the midst of all this noise and vibration. For 100 years, it seemed that Einstein was right. But in 2015, LIGO and VIRGO - gravitational wave detectors located at EGO (European Gravity Observatory in Washington and Louisiana) first recorded gravitational waves: signals from the merger of two black holes at a distance of about 1.3 billion light-years from Earth.
The discovery marked the beginning of a new field of astronomyand brought the Nobel Prize in Physics to researchers who worked on the project. This time, scientists compared the collision of supermassive black holes, since the LIGO detector first detected a burst of light, which previously seemed impossible, because black holes do not emit light.
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Researchers believe collision forceof two massive objects caused the newly formed black hole to slip through the gas of the accretion disk around the larger black hole. A press release from a study published in the journal Physical Review Letters says that it is the reaction of gas to acceleration that creates a bright flash that is visible through telescopes. A team of astronomers at the California Institute of Technology expects to see another surge from the same black hole in a few years, when it is projected to re-enter the accretion disk of the supermassive black hole.
The reason why looking for such surges is important,lies in the fact that they help in matters of astrophysics and cosmology. If we can again detect light from the confluence of other black holes, we will learn more about the origin of these mysterious objects.
Research co-author Mansi Castlely, associate professor of astronomy at the California Institute of Technology.
Both detectors and LIGO and VIRGO recordedperturbations in space-time in May 2019. Just a few days later, telescopes at the Palomar Observatory near San Diego noticed a bright flash of light coming from the same place in space. Researchers later looked at archival images of this area of the sky and noticed a splash. The outbreak slowly faded over the course of a month. The timeline and location coincided with the LIGO data. In the course of work, the team came to the conclusion that the surge is probably the result of the merger of two black holes, however, other options cannot be completely ruled out. Nevertheless, they managed to exclude the possibility that the burst occurred as a result of ordinary explosions in the accretion disk of a supermassive black hole, since before the burst, for 15 years, the disk behaved relatively calmly.
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Study of gravitational waves
In the future, researchers expect more of thesediscoveries. That's because in the next few years, a new gravitational-wave observatory - the Kamioki gravitational-wave detector (KAGRA), should begin work. With the help of KAGRA, LIGO and VIRGO, scientists expect to narrow the search for the location of massive collisions by three times. It will also help to improve the equipment of telescopes to more accurately detect these events causing gravitational waves and to detect the light emitted by them. According to the authors of the scientific work, the new global network of detectors can ultimately detect up to 100 collisions per year.