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An international team led by Matthew Liska of the Anton Pannekoek Institute of the University of Amsterdam 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. The research is publisched in the Monthly Notices of the Royal Astronomical Society.

This computer simulation shows that the inner regions of the gas disk (red) aligns with the black hole.
Computer simulation shows how the gas disk aligns with the black hole.

Among the findings, the team of computational astrophysicists from the University of Amsterdam, Northwestern University, and the University of Oxford found that the inner-most region of an accretion disk aligns with its black hole's equator.

Mystery

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.

Matthew Liska, a researcher at the University of Amsterdam's Anton Pannenkoek Institute for Astronomy, is the paper's first author.'These simulations not only solve a 40-year-old problem, but they have demonstrated that, contrary to typical thinking, it is possible to simulate the most luminous accretion disks in full general relativity,' Liska said. 'This paves the way for a next generation of simulations, which I hope will solve even more important problems surrounding luminous accretion disks.'

Publication details
'Bardeen–Petterson alignment, jets, and magnetic truncation in GRMHD simulations of tilted thin accretion discs.' By: M. Liska (UvA) , A. Tchekhovskoy (Northwestern University), A. Ingram (University of Oxford), M. van der Klis (UvA). In: Monthly Notices of the Royal Astronomical Society, Volume 487, Issue 1, July 2019, Pages 550–561, https://doi.org/10.1093/mnras/stz834