Northwestern University | 2019 Jun 06
For the first time, researchers prove 1975 proposition that accretion disks align with their black holes
An international team has constructed the most detailed, highest resolution simulation of a black hole to date. The simulation proves theoretical predictions about the nature of accretion disks -- the matter that orbits and eventually falls into a black hole -- that have never before been seen. ...
Among the findings, [researchers] found that the innermost region of an accretion disk aligns with its black hole’s equator.
This discovery solves a longstanding mystery, originally presented by Nobel Prize-winning physicist John Bardeen and astrophysicist Jacobus Petterson in 1975. At the time, Bardeen and Petterson argued that a spinning black hole would cause the inner region of a tilted accretion disk to align with its black hole’s equatorial plane.
After a decades-long, global race to find the so-called Bardeen-Petterson effect, the team’s simulation found that, whereas the outer region of an accretion disk remains tilted, the disk’s inner region aligns with the black hole. A smooth warp connects the inner and outer regions. The team solved the mystery by thinning the accretion disk to an unprecedented degree and including the magnetized turbulence that causes the disk to accrete. Previous simulations made a substantial simplification by merely approximating the effects of the turbulence. ...
Bardeen-Petterson Alignment, Jets and Magnetic Truncation in
GRMHD Simulations of Tilted Thin Accretion Discs ~ M. Liska et al