Astronomers with amazing accuracy foresaw the dance of a pair of black holes

US, WASHINGTON (ORDO NEWS) — Scientists incredibly accurately (up to several hours) predicted the movement of a pair of supermassive black holes. In addition, they tested the famous theorem that black holes have no hair.

The achievement is described in a scientific article published in the Astrophysical Journal Letters.

Dance of the giants

The central black hole of the OJ 287 galaxy, located 3.5 billion light years from Earth, is one of the most massive among the known to science. Its mass reaches 18 billion (!) Suns. Next to her, her companion, a black hole weighing 150 million suns, looks small.

This “baby” makes a complete revolution around his colossal girlfriend in about 12 years. Each time it crashes into a gas disk surrounding a central body. This collision generates more radiation than a trillion stars (by the way, there are ten times less of them in the Milky Way). For a short time, the system becomes four times brighter than usual.

The orbit of a small black hole shifts after each revolution. She turns and changes the slope relative to the gas disk. Therefore, the celestial body is immersed in a cloud of matter in different parts of its trajectory, and flashes occur irregularly. Sometimes a year passes between them, and sometimes ten.

Calculating when the next collision of a black hole with a gas disk occurs is an interesting task. It allows you to check how well scientists understand the physics of black holes.

Let us explain that the motion in such a system is much more complicated than, for example, the revolution of the Earth around the Sun. Newton’s law of gravity is no longer enough to correctly calculate the trajectory. We have to take into account the effects of Einstein’s general theory of relativity, including the radiation of gravitational waves. The distribution of mass inside the black hole also matters. Only with an accurate account of all these factors can we successfully predict when the next outbreak will occur.

In 2018 a group led by Lankeshwara Deem from Tata Institute of Fundamental Research in India has published an article in which predicted a time following the outbreak (31 July 2019) up to four hours.

Farewell gift “Spitzer”

Scientists were right. The outbreak really occurred at the appointed time with an accuracy of four hours, which the authors report in a new article.

Moreover, it was possible to observe this phenomenon almost by a miracle. On July 31, 2019, the OJ 287 galaxy was obscured by the Sun from all terrestrial and near-Earth space telescopes. Humanity simply would not have known about this outbreak, if not for the Spitzer infrared telescope.

This observatory was launched in 2003 and for more than 16 years of work brought a huge number of discoveries . But the apparatus gradually moved away from the Earth, and it became increasingly difficult to work with it. In mid-2019, Spitzer was already more than 600 times farther from our planet than the Moon. This was one of the main reasons why the telescope mission was completed in January 2020 .

But it was this huge distance that played into the hands of astronomers on July 31, 2019. The device in proud solitude surveyed OJ 287 from a different position, and the Sun did not bother him.

“The amazing success that we were able to capture the peak of the outbreak with” Spitzer “because no other tools created by man, were not capable of it at that particular moment in time”, – admits the first author Seppo Laine ( Seppo Laine is ) from California Institute of Technology.

Black holes don’t need hairdressers

This work helped experts test one of the extremely important statements about black holes.

As we already mentioned, when calculating the trajectory of a smaller black hole, one must take into account how the mass of the larger is distributed. In this, astronomers relied on a fundamental theorem that was deduced in the 1960s. She claims that a black hole cannot have any characteristics except mass, angular momentum, and electric charge. Two black holes in which these three parameters coincide cannot be distinguished from each other. This statement is often formulated in the form of the aphorism “Black Holes Have No Hair”, that is, individual characteristics.

This thesis is one of the most important in the physics of black holes. And so a couple of supermassive monsters in the OJ 287 galaxy helped observers verify this theoretical position.

Indeed, among other things, it follows from the theorem that a black hole is symmetric about the axis of rotation. It cannot have bulges and depressions on its surface (more precisely, the event horizon ). It was from this distribution of mass that the researchers proceeded. And their calculations brilliantly confirmed by the observations of “Spitzer”.

Thus, the illustrious space telescope gave mankind a farewell gift, allowing specialists to make sure that they really understand the physics of black holes, and, in particular, that the absence of hair theorem works.


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