Scientists Simulate Accretion Disk Flow Around Sagittarius A*International Business Times
Avaneesh Pandey December 27, 2016
Image and inset of region surrounding Sagittarius A*. Photo: Image: NASA/UMass/D.Wang et al. Inset: NASA/STScI.At the center of the Milky Way lies a supermassive black hole named Sagittarius A*. Around this black hole lies an accretion disk, composed of an orbiting cloud of gas, dust and plasma that is being slowly pulled inward due to gravitational attraction.
While this happens, massive bursts of energy — the result of the conversion of gravitational potential energy into radiation — are being released. However, scientists have observed that the radiation being emitted by the accretion disk around Sagittarius A* is much less than one would expect.
“So the question is, why is this disk so quiescent?” Matthew Kunz, an astrophysicist at Princeton University, and lead author of
a paper that describes a new model to simulate the complex processes taking place within the accretion disk, said in a statement.
The researchers, when they studied the Sagittarius A* accretion disk, found the plasma it contains is so hot that it is “collisionless” — the protons and electrons in it rarely, if ever, collide.
“This lack of collisionality distinguishes the Sagittarius A* accretion disk from brighter and more radiative disks that orbit other black holes,” the Princeton Plasma Physics Laboratory (PPPL) explained in the statement. “The brighter disks are collisional and can be modeled by formulas dating from the 1990s, which treat the plasma as an electrically conducting fluid.”
In order to accurately model the behavior of the accretion disk that orbits our galaxy’s supermassive black hole, the researchers used a method that tracked the motion and path of individual particles — rather than one that treats the motion of plasma as a macroscopic fluid.
In doing so, the researchers hope to create a model that better predicts the emission of radiation from black hole accretion at the galactic center, bringing the predictions in line with astrophysical observations made using NASA’s Chandra X-ray observatory.
“This kinetic approach could help astrophysicists understand what causes the accretion disk region around the Sagittarius A* hole to radiate so little light,” PPPL said. “Results could also improve understanding of other key issues, such as how magnetized plasmas behave in extreme environments and how magnetic fields can be amplified.”
https://www.yahoo.com/news/scientists-simulate-accretion-disk-flow-111547014.html
6 new categories and 72 new items added to the shop!
