Astronomers have described unusual dynamics in the binary system of a black hole and the usual star V404 Cygnus, in which the direction of the jet of emissions from a compact object changes on the scale of minutes. Such a rapid evolution is associated with the action of the relativistic dragging effect of reference frames and the noticeable angle between the spin of the black hole and the perpendicular to the disk from the falling matter, the authors write in the journal Nature.
One of the types of variable celestial objects are X-ray binaries - systems of two bodies with high luminosity in the X-ray range. The high-energy radiation of such an object arises in an accretion disk heated to high temperatures, which is formed from the matter of an ordinary star, flowing into a compact second component (this could be a black hole or a neutron star).
In some cases, in such systems, the formation of jets is observed - narrow jets of matter, which move almost at the speed of light from the poles of rotation of black holes. The direction of the jets does not change or changes slowly, but work under the direction of James Miller-Jones of the International Center for Radio Astronomy Research describes a case of extremely rapid variability of the direction of a jet in the V404 Cygnus system located at a distance of 2.4 kiloparsecs.
The data obtained by the authors using very long baseline radio interferometry (which made it possible to obtain the first ever image of a black hole shadow) made it possible to study in detail the dynamics of the system during two flares in 2015, which lasted about a week. During the first observation session, when the scientists worked with a long exposure of 4 hours, only a blurry picture was obtained. The authors had to change the approach and accumulate data in just 70 seconds, which allowed them to capture the changes and simulate the animation of the jet.
Scientists suggested explaining the observed behavior by the Lense-Thirring effect, also called the dragging of frames of reference. This phenomenon is possible in the case of rotating massive bodies, which can entrain space-time itself with their rotation, because of which all objects around are also forced to move in a circle in the same direction.
In this case, the axis of rotation of the black hole does not coincide with the rotation of a thin and flat accretion disk, which is why an inclined part, like a donut, forms in its center. It "swells" due to high heating and radiation pressure, but it is rather small in size: several thousand kilometers versus 10 million kilometers of the entire disk. Since the jet is formed in the immediate vicinity of the black hole, the tilted inner part redirects it in different directions.
The authors could not offer another explanation for the precession of the jet in this case, however, they note that in the study of active galaxies with much more massive black holes, indications of the presence of a change in the direction of the jets are also recorded. Other works by astrophysicists have tried to explain this existence of binary supermassive black holes at the centers of some galaxies, but new research suggests that this may not be the only possible explanation.
One of the main unsolved problems in black hole astrophysics is the question of the origin of jets. Recently, the Russian satellite Radioastron examined the structure of a jet near a supermassive black hole, the formation of a jet was also observed in V404 Cygnus, and theorists proposed a way to estimate the rotation of black holes based on studies of jets.
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