Astronomers are right now watching the distant star circling in a death dance around a big black hole. The distance between the objects is only about 2.5 times greater than the distance between the Earth and the Moon. Being so close to one of the most deadly astronomical objects in the universe, the star makes a complete revolution around the black hole in just half an hour. For comparison: for a complete revolution around our relatively small planet, our moon, the moon, takes an average of about 28 days, while its speed is about 3683 kilometers per hour. All this suggests that the star revolves around the black hole just at an insane speed.
Based on data collected by a network of telescopes used for deep space exploration, the team of astronomers carried out calculations of the X-ray emission created by a double star system called 47 Tuc X9 located in one of the star clusters about 14,800 light-years away.
It should be noted immediately that astronomers know about the existence of this “pair” for a relatively long time – the system was first discovered in 1989, but only now the scientists have a complete picture of what is actually happening there.
“For a long time it was believed that the X9 system consists of a white dwarf and a sun-like companion star with a small mass, from which it sucks the matter,” researcher Arash Bahramian says.
Usually, binary systems of stars with such temperamental relations are included in the category of cataclysmic stars. However, in 2015, it became clear that the white dwarf companion is a black hole, and not a sun-like star, which, in turn, led scientists to reconsider some of the hypotheses previously adopted.
Returning to the study of this system, astronomers with the help of the space telescope “Chandra” confirmed the presence near the star of a certain amount of oxygen. Previously, scientists already found white dwarfs with an oxygen atmosphere, so, no doubt, they were confident that they had found the right goal. However, instead of the expected picture, where a white dwarf would tear apart another star, astronomers have witnessed that the victim is the white dwarf himself, while the role of the villain is played by a black hole sucking gas out of it.
In themselves, white dwarfs are a type of superdense star objects, which are essentially the remains of stars (imagine an object with the mass of our Sun, but with the size of our Earth). Therefore, in order to draw matter out of it, the object will need to possess a really powerful force of gravity.
“We think that the star has lost the reserves of its gases under the influence of a black hole for tens of millions of recent years and has now lost most of its mass,” says researcher James Miller-Jones of the Australian University of Curtin.
However, the most interesting news was due to the fact that on the basis of regular changes in the intensity of X-ray radiation stars, scientists were able to establish that the white dwarf takes only 28 minutes to complete the turn around the black hole, which makes him the champion among such “dirty dances”.
“Prior to this discovery, the nearest star to the black hole was an object located in the MAXI J1659-152 system. Its orbital period is only 2.4 hours, “continues Miller-Jones.
If (and this really can be), both black holes in their systems have the same mass, then the radius of the star’s orbit in the MAXI J1659-152 system will then be three times larger than the star of the X9 system. The distance between objects in the X9 system is 1 million kilometers, which is about 2.5 times the distance from us to the Moon. Further calculations say that the star in half an hour passes a distance of about 6.3 million kilometers, which gives us a speed of 12,600,000 kilometers per hour. And this, in turn, is about 1 percent of the speed of light.
Despite the impressive figures, the article of researchers at the moment is still only waiting for the review by the community of physicists on the site arXiv.org. Nevertheless, the information presented in it can be of practical importance in the future.
“The discovery of such a rare type of black holes is important, because they can not only tell us about the final days of life of stars turning into supernovae, but also because they continue to play their role in the evolution of other stars after their death,” comments Gereint Lewis from Sydney University.
Scientists note that our “space lovers” are not going to collapse in the near future and continue their deadly dance without the convergence of a white dwarf to the belly of a black hole. Moreover, there is a suspicion that earlier both objects were at a closer distance to each other or at least a white dwarf had an even higher rotation speed. To dominate the gravity of a black hole above the gravitational force of the whiteest dwarf, the objects need to be closer to each other, but they do not intend to approach each other yet. And yet eventually all the material of the star will ultimately undoubtedly be absorbed by a black hole, scientists say.
“Ultimately, a white dwarf will lose so much matter that its mass will become equivalent to the mass of an ordinary planet,” says researcher Craig Heinke. “If, after that, he continues to lose his mass, he will eventually completely evaporate.”
For scientists of the future, such news can not but cause joy, as this will be an excellent opportunity for direct observation and study of gravitational waves. At the moment, even the most powerful laser interferometer of the laboratory for monitoring gravity waves can not detect the weak pulsation emitted by the X9 star, however in the future the technologies will undoubtedly allow scientists to determine low frequency waves. In addition, no one denies the possibility that by that time we will be able to find even more interesting cataclysmic stars moving at even higher speeds.