An international research team, led by the Indian Space Research Organization (ISRO) and NASA, has just discovered in a 4U 1630-47 black hole binary system that rotates almost to the maximum speed permitted by the theory of General Relativity. from Einstein. In fact, the rotation is so fast that the object will force the surrounding space to rotate next to it. According to scientists, who use the Indian AstroSat satellite and the Chandra X-ray Observatory, from NASA, and whose work will be published soon in the Astrophysical Journal, studying black holes with high turning speeds is the most important to place testing our theory of the Universe, including Relativity itself. It all began in 2016, when AstroSat found a black hole in a binary system (two star objects orbiting each other) 4U 1630-47. From the first moment, a series of violent outbreaks in the X-ray range attracted the attention of researchers. Shortly after, the Chandra Observatory confirmed the results and it became clear that this particular black hole was unlike the others.
X-ray emissions from black holes occur because the surrounding material (mostly gas and dust) is deposited and "consumed" by it. This emission allows researchers to realize that the intended black hole, whose mass is ten times that of our Sun, rotates on itself at a dizzying speed. The rotation rate of black holes can oscillate between two values, 0 and 1. And a black hole 4U 1630-47 shows a rotation rate of 0.9, which is almost equivalent to the speed of light. The fact that makes the researchers gape, because Einstein's theory implies that if the black hole can spin so fast, then it will be able to make the space itself rotate next to it. So far, of the twenty holes that are known in our galaxy, it is only possible to measure the rotation of the other four. And the 4U 1630-47 system is, without doubt, the fastest of all. Scientists believe that, if what we know about black holes is true, the combination of factors such as rotational speed, material entering them and high temperatures can be key to understanding how galaxies form.
How do you know how fast they spin?
The mass and speed of rotation are the two main characteristics that characterize black holes. But while the dough can count easily, thanks to the seriousness of the produce, finding out the rate of rotation is something far more complicated. In the words of Mayukt Pahari, the lead author of the study, "measurement of rotational speed is very difficult, and it is only possible to carry it out by observing high-quality X-rays from the binary star system, in that black holes absorb material from their companion stars." If the calculation is correct, the 4U 1630-47 black hole binary system can be the key to knowing how these extraordinary objects affect the space itself. And it reveals, in passing, an unknown process that leads to galaxy formation.