Image of a relativistic jet in close proximity to a black hole in the M87 galaxy. Source : R.-S. Lu (SHAO), E. Ros (MPIfR), S. Dagnello (NRAO/AUI/NSF).
For the first time, scientists have published an image that shows both a black hole and a jet born near it. A radio image of a relativistic jet emanating from a supermassive black hole in the M87 galaxy in the constellation Virgo appeared in an article by an international team of researchers in the journal Nature.
The M87 galaxy is 53 million light-years away. Its mass is several hundred times greater than the mass of our galaxy. At the center of the galaxy is a black hole that is several billion times heavier than the sun. In 2019, the Event Horizon Telescope image of this black hole became a worldwide sensation. The image was obtained by radio interferometry. The essence of this method is that the signals from observations received at radio telescopes in different parts of the globe are brought together. Taking into account the phase of the signal (in addition to the amplitude) allows you to restore the entire picture in detail. The resolution of such observations is the higher, the greater the distance between the individual radio telescopes.
It is impossible to see the black hole itself through a telescope, but you can see its accretion disk, that is, matter falling on it rotating around the black hole. It is strongly heated due to friction and therefore begins to glow, due to which it becomes noticeable in the optical and radio ranges. The picture of such an accretion disk was seen in the M87 Event Horizon Telescope galaxy in 2019 at a wavelength of 1.3 mm.
A new achievement of scientists is that with the help of another interferometric instrument – GMVA (Global Millimetre Very-long-baseline interferometry Array, a global network of millimeter interferometry with a very long baseline) – at a wavelength of 3.5 mm, it was possible to discern a radio signal from the very foundation of the relativistic jet emanating from the vicinity of the black hole. A jet is a powerful stream of ionized matter that is “thrown out” by a black hole. In a jet, matter moves at speeds comparable to the speed of light, which is why the jet is called relativistic. Due to the deceleration of the jet matter, X-rays are generated. The jet is apparently formed from the matter of the accretion disk due to interaction with the magnetic field of the black hole, but the exact mechanisms of the formation of the jet are still unknown.
The resolution of GMVA is worse, but it works at a different wavelength and sees other details that the Event Horizon Telescope did not see. GMVA was able to see the radio signal at the very "base" of the jet, where the jet is born. Thus, for the first time, scientists saw the structure of a jet in the immediate vicinity of a black hole. This jet is an extremely powerful phenomenon, it extends from the center of the M87 galaxy for thousands of light-years and is visible in various ranges.
This is not the only improvement in the image of the “heart” of the M87, which has been achieved recently. Thanks to the use of neural networks , it was possible to significantly improve the image quality of the M87 accretion disk. The next step in their research, astronomers see the application of proven methods to look at the black hole located at the center of our Galaxy.