Explanation found for X-ray radiation from black holes | Science & Technology

Using detailed supercomputer simulations, researchers at the University of Helsinki modeled the interactions between radiation, plasma, and magnetic fields around black holes. It was found that the chaotic movements, or turbulence, caused by the magnetic fields heat the local plasma and make it radiate.

Focus on the X-ray radiation from accretion disks

A black hole is created when a large star collapses into such a dense concentration of mass that its gravity prevents even light from escaping its sphere of influence. This is why, instead of direct observation, black holes can only be observed through their indirect effects on the environment.

Most of the observed black holes have a companion star, with which they form a binary star system. In the binary system, the two objects orbit each other, and the matter of the companion star slowly spirals into the black hole. This slowly flowing stream of gas often forms an accretion disk around the black hole, a bright, observable source of X-rays.

Since the 1970s, attempts have been made to model the radiation from the accretion flows around the black holes. At the time, X-rays were already thought to be generated through the interaction of the local gas and magnetic fields, similar to how the Sun’s surroundings are heated by its magnetic activity via solar flares.

“The flares in the accretion disks of black holes are like extreme versions of solar flares,” says Associate Professor Joonas Nättilä. Nättilä heads the Computational Plasma Astrophysics research group at the University of Helsinki, which specializes in modeling precisely this kind of extreme plasma.

Radiation-plasma interaction

The simulations demonstrated that…