Researchers have conducted groundbreaking simulations of rotating black holes based on the principles of general relativity. Their work revealed that the ultraluminous accretion disk, which is a swirling mass of gas around a black hole, displays a precessional motion influenced by the black hole’s spin. This discovery suggests that the spin of the black hole may be the main factor driving the regular brightness changes seen in these ultraluminous accretion disks.
Researchers at University of Tsukuba have carried out groundbreaking simulations of rotating black holes based on general relativity principles. They found that the ultraluminous accretion disk (the gas spiral surrounding a black hole) shows a precessional motion that is influenced by the spin of the black hole. This discovery indicates that this spin might be the key factor responsible for the periodic brightness changes identified in these ultraluminous accretion disks.
Gas moves around a black hole due to its powerful gravitational pull, forming an accretion disk. These disks are among the most efficient sources of energy conversion in the universe and emit light and jets of plasma. When a black hole spins, the accretion disk can behave like a top that wobbles. Precessional motion has been observed in less luminous accretion disks, but it wasn’t clear if the same effect occurs in ultraluminous disks that emit significant radiation.
Researchers at University of Tsukuba carried out large-scale simulations involving radiation and electromagnetic hydrodynamics based on general relativity. They demonstrated for the first time that the precessional motion of a tilted ultraluminous accretion disk is due to the black hole’s spin. Additionally, this wobbling motion changes the direction of the jets and radiation produced by the black hole, suggesting that the spin could be responsible for the periodic brightness variations seen in ultraluminous accretion disks—something that had been previously unknown.
In the future, the researchers plan to confirm whether black holes are indeed spinning by comparing long-term simulation results with observational data. This groundbreaking work is set to enhance our understanding of the effects of black hole spin on cosmic events and contribute significantly to the verification of the spacetime framework of black holes and general relativity.
This research received support from JSPS KAKENHI Grant Numbers 23K03445(Y.A.), 21H01132(R.T.), 21H04488, 18K03710(K.O.). It was also funded by MEXT through the “Program for Promoting Researches on the Supercomputer Fugaku” (Structure and Evolution of the Universe Unraveled by Fusion of Simulation and AI; Grant Number JPMXP1020230406). Computational resources were provided by supercomputer Fugaku (RIKEN Center for Computational Science, Project ID: hp230204, hp230116), ATERUI II (National Astronomical Observatory of Japan), Oakforest-PACS (the University of Tokyo and University of Tsukuba), and Wisteria/BDEC-01 Odyssey (the University of Tokyo).
