An international team of scientists, including researchers from the FIAN, MIPT and the Moscow State University. M.V. Lomonosov obtained an unprecedentedly accurate image of the formation of a plasma in the vicinity of a massive black hole. The structure of the jet was not able to achieve so far. The new data mean that theorists will have them reconsider. The corresponding article is published in Nature Astronomy.
In the centers of almost all known galaxies, there are black holes, the mass of which is millions to many billion times larger than that of the Sun. Some of these massive black holes emit so-called relativistic jets, whose name comes from the fact that the component of their plasma moves at a speed close to the speed of light. Such plasma jets, also called jets, can stretch for many hundreds of thousands of light years. How exactly they are formed, why do some black holes have jets and others do not, the question over which astrophysicists and astronomers have been struggling for many years. One of the main difficulties, in this case, was close to their origin. Without this, it was impossible to compare the real picture with that.
There are two competing ideas that have been introduced for almost a third of a century ago. The first is the Blandford-Znajek model. The black hole, as far as we know, always rotates quickly. It does not absorb matter directly, first its gravity forms. But due to its rotation, part of the matter from the disk is not absorbed, but on the contrary, it is ejected, thus gaining a high speed. According to the Blandford-Znajek model, that of the black hole (from the accretion disk), which is not sucked into it, is thrown out and forms a narrow jet. He receives energy from the black hole itself, through gravitational interaction.
The second model, Blanford-Payne, in her jet is not ejected from the immediate vicinity of the black hole, but from the accretion disk, which also rotates and ejected matter. Most astronomers preferred the first model, Blanford-Znaek, and believed that the jets formed the most central supermassive black hole.
Within the framework of the new work, the researchers studied the vicinity of a supermassive black hole in the center of Perseus A. The Russian astronomers combined data from the 40 largest terrestrial radio telescopes around the world and the Russian space radio telescope Radioastron. It is located on the Earth, which makes it possible to achieve ultra-high resolution. Signals of individual telescopes were synchronized with an atomic clock. As a result, the researchers were able to obtain a detailed image of the base of the jet ten times closer to the boundary of the black hole.
The structure of the jet, revealed by radio emission from its plasma, speaks in favor of the fact that the accretion disk is at least partially involved in the formation of jets and possibly is their main source. This means that until now most astronomers have made mistakes in this respect, and the Blanford-Payne model is closer to reality than the Blandford-Znajek model.
To understand what exactly is the source of the jet, it was possible due to the unprecedented high resolution of the image taken in the radio range – it was 12 light days for a distance of 230 million light years. This resolution is allowed to see that the jet flows immediately, at its very base. This is unrealistic if the substance of the jet is ejected from a black hole – there is simply not enough room for the wide base of the jet and strong gravitational fields. According to the new observations, the width of the jet, at the very bottom of the black hole, and therefore it cannot be generated by itself. Such a jet structure can only be provided if the accretion disk played an important role in its formation.
RadioAstron has been operating in orbit since 2011. It is equipped with a 10-meter mirror, so large that it could be fully deployed only in space (there are simply no rockets with a sufficiently large head fairing). RadioAstron realizes a record angular resolution up to several microseconds of the arc, equivalent to a radio telescope with a diameter of 350,000 km – almost the distance between the Earth and the Moon