Supercomputers give scientists superpower to unlock black hole disk dynamics

In the center of almost every galaxy lies a mysterious celestial object: the black hole. These cosmic behemoths are so dense that nothing, not even light, can escape their gravitational pull.

But while they may seem impenetrable, their effects can be observed through the swirling disks of gas that surround them.

A team of researchers at Tohoku and Utsunomiya Universities have conducted an in-depth study to understand the complex turbulence within these accretion disks.

Using powerful supercomputers, they’ve conducted the highest-resolution simulations ever of these cosmic structures.

“Accurately simulating the behaviour of accretion disks significantly advances our understanding of physical phenomena around black holes. “It provides crucial insights for interpreting observational data from the Event Horizon Telescope,” said Yohei Kawazura.

Use of supercomputers

Black holes cannot be directly detected by ground or space-based telescopes. But the accretion disks of gas, plasma, and dust that orbit them emit detectable electromagnetic radiation, allowing astronomers to infer the presence of black holes.

This process creates intense turbulence, which has been a challenging phenomenon to study. Previous simulations had been limited by computational power, but this new research has broken new ground.

The researchers leveraged the computational power of supercomputers like RIKEN’s “Fugaku” and NAOJ’s “ATERUI II. Interestingly, Fugaku held the title of the world’s fastest computer until 2022.

These two combined allowed the researchers to conduct simulations at unprecedentedly high resolutions.

Thanks to the combined power, the researchers were able to reproduce for the first time the “inertial range connecting large and small eddies in accretion disk turbulence.”

The inertial range in accretion disk turbulence refers to the specific range of scales or sizes of eddies, or swirling patterns, that exist within the turbulent flow of the disk. Moreover, accretion disks rely on turbulence to generate viscosity, a property that allows material to flow and be transported toward the central black hole.

Insights into turbulence in accretion disks

Apart from this, the simulations revealed that “slow magnetosonic waves” dominate the inertial range of turbulence in accretion disks. This wave propagates through a magnetized plasma.

This finding suggests that these waves carry the majority of the energy within this specific range of scales.

“This finding explains why ions are selectively heated in accretion disks. The turbulent electromagnetic fields in accretion disks interact with charged particles, potentially accelerating some to extremely high energies,” the press release explained.

Interestingly, the team noted that these slow waves carry “about twice the energy of Alfvén waves.”

Alfvén waves are a type of wave that arises in a plasma due to the interaction between the magnetic field and the electric currents within it. As per the press release, the Alfvén waves mostly dominate solar wind turbulence.

The researchers highlight that this study has significant implications for our understanding of black holes and their environments. It will help them to interpret data from telescopes like the Event Horizon Telescope, which has captured images of black holes.

“This advancement is expected to improve the physical interpretation of observational data from radio telescopes focused on regions near black holes,” they noted in the press statement.

Recently, the Event Horizon Telescope collaboration recently announced the highest-resolution observation ever made from Earth of a black hole. With this achievement, EHT aims to take 50% sharper black hole images in the future.

The findings were published in the journal Science Advances.