The mass of a black hole

There is no scale to weigh black holes. However, astrophysicists from the Moscow Institute of Physics and Technology have come up with a new way to indirectly measure the mass of a black hole, while confirming its existence. They tested the new method, reported in the Monthly Notices from the Royal Astronomical Society, on the active galaxy of Messier 87.

Active galactic nuclei are among the brightest and most mysterious objects in space. A galaxy is considered active if it produces a long beam of matter and energy directed outwards. Known as a relativistic jet, this phenomenon can not be explained by the stars of the galaxy. The current consensus is that jets are produced by a kind of "engines", called galactic nuclei. Although their nature is poorly understood, researchers believe that a rotating black hole could fuel an active galaxy.

Messier 87 in the constellation Virgo is an active galaxy closest to the Earth and best studied. It has been observed regularly since 1781, the year of its discovery as a nebula. It took a while before astronomers realized that it was a galaxy and that its optical jet – discovered in 1918 – was the first to be observed.

The structure of the Messier 87 jet has been carefully studied, with mapping of its plasma jet velocities and measuring the density of the temperature and the number of particles near the jet. The limits of the jet were studied with such precision that the researchers discovered that it was inhomogeneous throughout its length, thus changing from parabolic to conical shape. Originally discovered as an isolated case, this effect was confirmed later for a dozen other galaxies, although M87 remains the clearest example of the phenomenon.

The large number of observations makes it possible to test hypotheses concerning the structure of active galaxies, including the relationship between the rupture of the jet shape and the gravitational influence of the black hole. The behavior of the jets and the existence of the supermassive black hole are two sides of the same coin: the first can be explained in terms of the second, while the theoretical models of the black holes are tested via observations at the same time. jet.

Astrophysicists have exploited the fact that the jet limit consists of segments of two distinct curves and used the distance between the core and jet break, as well as the width of the jet, to indirectly measure the mass and the spin of the hole black. To this end, MIPT scientists have developed a method combining a theoretical model, computational calculations and telescope observations.

The researchers are trying to describe the jet as a flow of magnetized fluid. In this case, the shape of the jet is determined by its electromagnetic field, which in turn depends on various factors, such as the speed and charge of the particles of the jet, the electric current in the jet and the speed at which the black the hole increases the material. A complex interaction between these characteristics and the physical phenomena gives rise to the observed rupture.

There is a theoretical model that predicts the break so that the team can determine what mass of black holes results in the model reproducing the observed shape of the jet. This provided a new model for estimating black hole mass, a new measurement method, and confirmation of the assumptions underlying the theoretical model.

"The new independent method of estimating the mass and rotation of black holes is the key result of our work, and although it is comparable in accuracy to existing methods, it has the advantage of bringing us closer together. of the final goal., refining the parameters of the "engine" central to better understand its nature, "said Elena Nokhrina, lead author of the article and deputy director of the laboratory MIPT involved in the study .