When a black hole actively feeds, something strange can be observed: enormously powerful plasma jets from their poles at speeds close to the speed of light.
Given the intense gravity interactions in the game, it's just how these jets form a secret. Now, a team of physicists has come up with an answer using computer simulations – particles that appear to have "negative energy", deprive the black hole of energy, and redirect it to the jets.
And this theory has for the first time united two different and seemingly incompatible theories of how to extract energy from a black hole.
The first process is called the Blandford-Znajek process and describes how a black process is described. The magnetic field of the hole can be used to extract energy from the rotation.
As the material in the accretion disk swings ever closer to the event horizon, it is theoretically assumed that it is increasingly magnetized and generates a magnetic field. In this field, the black hole acts as a rotating conductor, inducing a voltage between the poles and the equator. This voltage is discharged by the poles as jets.
The second is called the Penrose Process and is based on conservation of momentum and not on magnetism. The rotational energy of a black hole is not within the event horizon, but in a region called the ergosphere, which comes into contact with the event horizon at the poles.
After the Penrose process, when an object within that region broke apart, one piece being thrown against the black hole and the other outward. Towards turning the black hole, the outward-bound piece would come out of the rotation with more energy. This creates a kind of "negative energy".
Both scenarios are convincing, but until now we were not sure of the right answer.
"How can the energy from the rotation of a black hole be made to make jets?" said theoretical physicist Kyle Parfrey of the Lawrence Berkeley National Laboratory. "This has been a question for a long time."
The team designed a simulation of collision-free plasma (where particle collisions do not play a major role) in the presence of a strong gravitational field of a black hole. They also provided for the generation of electron-positron pairs in the electric fields, which allowed more realistic plasma densities.
The resulting simulation naturally produced the Blandford-Znajek process ̵
But also produced a variation of the Penrose process. Due to relativistic effects, some particles appeared to have "negative energy" as they disappeared into the black hole – slowing the rotation of the black hole to a tiny fraction.
"If you were right next to a particle you would not see anything weird about it, but to a distant observer it looks like it has negative energy," said Parfrey New Scientist .
"They are still left In this strange case, when it falls into the black hole, this leads to a decrease in mass and rotation."
The effect did not contribute much to the overall energy production, Parfrey noted, but it's possible that it's somehow related to the electrical currents that twist the magnetic fields.
Simulation also lacks some components, such as the accretion disk, and the physics of positron electron generation is not as detailed as it could be. The team will work on an even more realistic simulation to examine the process in more detail.
"We hope to provide a more consistent picture of the entire problem," said Parfrey.
The team's research has been published in the journal Physical Review Letters and can be read in full in arXiv.