The so-called supermassive black holes, located in the middle of galaxies, store a gigantic amount of energy. A team of physicists from the Institute of Physics in Opava, prof. Zdeněk Stuchlík, Arman Tursunov and Martin kološ, describe the mechanisms of generating such energy. In their new scientific work, they focused on the consequences of the so-called Penrose processes, ie on the description of obtaining energy from the immediate vicinity of black holes. As early as 1969, the British physicist Roger Penrose (b. 1931), winner of the Nobel Prize in Physics in 2020, discovered that a vast amount of energy could be gained around a rotating black hole through a phenomenon known as "frame-dragging".
Huge amount of energy hidden in a magnetic fieldIn 1977, physicists Roger Blandford and Roman Znajek came up with the theory that a rotating black hole in a magnetic field could provide energy. The lines of the magnetic field twist due to the frame dragging and create an effective electric charge. As the charge discharges, the rotational energy of the black hole is extracted out. If we consider a typical supermassive black hole (about a trillion Sun masses), that would give an energy of about 10^(55) Joules, which is a hundred trillion times (or 14 orders of magnitude!) more than how much energy is needed across the globe at the moment. This is however only one of the processes, the so-called magnetic, whose efficiency increases with the mass of the black hole and the intensity of the surrounding magnetic field.
"Rebellious" particles force a black hole to glow"A black hole can only release energy through the radiation of a charged particle, from a shell we call the ergosphere. This is a zone of a black hole above the event horizon, from which particles can still escape," describes Dr. Arman Tursunov, one of the co-authors of the work. He explains that for black holes to release energy in this way, the black hole must rotate. "We don't see black holes directly, but we assume they rotate, because that's the nature of every object in the universe. Around the rotating black holes, simply speaking, "rebellious" charged particles - those that do not move in the direction of the black hole's rotation - become energy carriers, accelerate, and escape. As a result of the law of conservation of energy, the black hole itself "suffers" and this results in a slight slowdown in its rotation." Such particles enter the vicinity of black holes from crumbling objects - the more material is in the vicinity of a material black hole, the greater the source of radiation energy the black hole becomes.