New simulations led by researchers working at the Department of Energy’s Lawrence Berkeley National Laboratory, or Berkeley Lab, provide insight on how black holes launch plasma jets — beams of ionized gas — into space.
According to the study, these plasma jets are generally thought to be driven by the magnetic fields surrounding a rotating black hole. This process is generally studied using the fluid approximation of plasma, which limits the amount of data collected.
“The idea is that every kind of black hole — from relatively small ones …to super massive black holes like the one in the center of our galaxy — has been observed to power these jets,” said Kyle Parfrey, study co-author and a senior fellow in the NASA postdoctoral program at the Goddard Space Flight Center. “The question is: how are these jets produced?”
Parfrey added that the most difficult task in answering this question is the plasma itself. According to the study, though liquid plasma has furthered the understanding of black hole accretion and jet production, it does not account for the creation of electron and positron pairs, which supply plasma jets around a black hole.
Alexander Philippov, study co-author and associate research scientist at the Flatiron Institute’s Center for Computational Astrophysics, added that the team’s simulations were the first to code collisionless plasma. According to Philippov, in collisionless plasma, low-density particles don’t find “partners” to collide with, making it harder to simulate.
“By incorporating collisionless plasma into the computer simulation, we were the first to use the right conditions to simulate the mechanics of how these jets extract energy from a black hole,” Philippov said. “It then provides a more complete theoretical understanding on how the jets are launched.”
Another major result of the study is the discovery of “exotic” particles found inside a black hole’s ergosphere, a region where all particles are forced to rotate in the same direction as the black hole. A large population of these “negative energy” particles were found — something that Parfrey said had not been able to be studied before.
Parfrey added that these particles were observed to extract the black hole’s energy and slow down its rotation as they cross the event horizon — the point where the gravitational pull of a black hole cannot be escaped.
“There are two large projects called the Event Horizon Telescope and GRAVITY, which aim to look at the accretion flow around the black hole at the center of our galaxy with enough resolution to actually make images,” Parfrey said. “Because of this accretion flow’s low density, you would need to use plasma simulations like the ones we’ve developed to study it realistically.”
