Visualization of general relativistic plasma simulation without collision. Image: Parfrey / LBNL
Researchers used one of the world's most powerful supercomputers to better understand how high-energy plasma streams escape the intense gravity of a black hole that absorbs everything else in its path – including light.
Before the stars and other things crossed the point of a black hole without a return – a boundary known as the "horizon of events" – and the black hole is swallowed, they begin to rotate in a black hole rotation. The question that physicists held for decades was how some energy managed to escape the process and get into the streams of plasma that travel through space near the speed of light.
As detailed in an article published last week in Physical Revision Letters, energy department researchers and the University of California at Berkeley used a supercomputer at DoE Lawrence Berkeley National Laboratory to simulate jet plasma electrically charged gas.
The simulation eventually compared two decades-old theory that attempt to explain how energy can be obtained from a rotating black hole.
The first theory describes how the electrical currents around a black hole are rotated by a magnetic field to form a current known as the Blandford-Znajek mechanism. This theory assumes that the material captured in the gravity of the rotating black hole will become more magnetized, the closer it gets to the event horizon. The black hole behaves like a massive wire that rotates in a huge magnetic field, causing the energy difference between the poles of the black hole and its equator. This energy difference then dissipates as nozzles at the poles of a black hole.
The second theory described the Penrose process, in which the particles approaching the horizon of the black hole events collapsed. In this scenario, one half of the particles will fire from the black hole and the other half of the particle bears negative energy and falls into the black hole.
"There is an area around a rotating black hole called ergosphere inside of which all particles are forced to rotate in the same direction as a black hole," said Kyle Parfrey, principal author of the book and theoretical astrophysicist at NASA, told me in an e-mail. "In this area it is possible for particles to have a negative effect in some ways if they try to bypass the rotation of the hole."
In other words, if one half of the partitioned particles are triggered against rotation of the black hole, the momentum of momentum or rotation of the black hole is reduced. But this rotational energy must go somewhere. In this case, it converts to the energy that drives the other half of the particle from the black hole.
According to Parfrey, Penrose's process, observed in his simulations, was somewhat different from the classical particle split situation described above. Rather than particle cleavage, the charged particles in the plasma act by electromagnetic forces, some of which are driven against the rotation of the black hole on the negative energy path. In this sense, Parfrey told me that they are still considered Penrose's type of process.
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The surprising part of the simulation Parfrey told me is that it seems to create a bond between the Penford process and the Blandford-Znajek mechanism, which he had never seen before.
Creating a magnetic field twist that extracts energy from a black hole in the Blandford-Znajek mechanism requires an electric current carried by particles within the plasma, and a large number of these particles have the negative characteristics of the Penrose process energy characteristics.
"So it seems that at least in some cases these two mechanisms are linked," Parfrey said.
Parfrey and his colleagues hope their models will provide the much needed context for the Event Horizon binoculars, a series of binoculars designed to directly portray the horizon of events where these plasma nozzles create. Until this first frame was created, however, Parfery said he and his colleagues wanted to improve these simulations in order to better adapt to the current observations.