A groundbreaking study led by Northwestern University has revealed that supermassive black holes consume surrounding material at a much faster rate than previously believed. The study, published in The Astrophysical Journal, employed high-resolution simulations to analyze the eating habits of black holes. The simulations showed that black holes tear apart the whirlpool of gas, or accretion disk, that surrounds them by twisting space-time, resulting in the formation of inner and outer subdisks. The black holes then consume the inner ring of the disk before the debris from the outer subdisk refills the gap left behind, repeating the cycle rapidly over a few months. This discovery challenges previous assumptions that black holes eat slowly.
The new research offers insights into the behavior of quasars, which are some of the brightest objects in the night sky. Quasars, which are fueled by black holes consuming gas from their accretion disks, often flare up and fade suddenly without explanation. The quick brightening and dimming observed in quasars are consistent with the destruction and replenishment of the inner regions of the disk, as suggested by the simulations.
The simulations also debunked a conventional assumption made by previous researchers that accretion disks are orderly and aligned with the black hole’s rotation. Instead, the simulations revealed that the gas feeding the black holes may not necessarily be aligned with the black hole’s rotation, leading to a drastic change in the overall picture. The study’s high-resolution simulations demonstrate that black hole surroundings are more turbulent and messy than previously thought.
To conduct the simulations, the researchers utilized Summit, one of the world’s largest supercomputers located at Oak Ridge National Laboratory. By incorporating gas dynamics, magnetic fields, and general relativity, the team was able to construct a more realistic model of a black hole. The simulations revealed that the spinning black holes dragged the surrounding space-time, causing the entire accretion disk to warp and collide, resulting in bright shocks that drove material closer to the black hole. As the warping intensified, the innermost region of the disk broke apart and evolved independently from the rest of the disk.
The tearing region between the inner and outer subdisks is where the feeding frenzy of the black hole occurs. The black hole’s rotation competes with the friction and pressure inside the disk, resulting in the ripping and pushing of the inner disk towards the black hole. The empty inner region is then refilled by the outer disk due to the black hole’s gravity. This cycle provides a potential explanation for the phenomenon of “changing-look” quasars, which appear to turn on and off within a matter of months.
The new simulations provide valuable insights into the mysteries of black holes and may help astrophysicists understand how gas feeds black holes, how long accretion disks last, and what the observed light from telescopes should look like. The study was supported by the U.S. Department of Energy and the National Science Foundation.