Astrophysical turbulence

International team produces the world’ s highest resolution simulation of astrophysical turbulence.

Quantum physicist Richard Feynman once called turbulence “the most important unsolved problem of classical physics”.

Now, in a study published in

Nature Astronomy, Australian and German scientists have used the computing power of the Leibniz Supercomputing Centre (LRZ) in Germany to probe how turbulence shapes the interstellar medium, and thus helps form stars and planets.

“Turbulence is a key ingredient for star formation,” says co-lead author Cristoph Federrath, an astrophysicist from the Australian National University.

“It controls the pace of star formation, stirring up gas and slowing down the action of gravity, which – without turbulence – would make stars form a hundred times quicker than observed.

“The formation of stars powers the evolution of galaxies on large scales and sets the initial conditions for planet formation on small scales.”

Turbulence itself can take a range of speeds, from large-scale supersonic motions (faster than the speed of sound) to smaller subsonic scales. To understand this transition from supersonic to subsonic, Federrath and team created the largest-ever simulation of supersonic turbulence. This involved using a massive amount of computing power to solve the complex equations of gas dynamics over a range of scales – modelling the large-scale phenomena happening faster than the speed of sound, as well as accurately capturing the details of the smaller, slower dynamics.

“With this simulation, we were able to resolve the sonic scale for the first time,” Federrath says.

The results of the simulation closely align with theoretical predictions, he suggests, but with subtle differences that will lead to further refinements of starformation models.

“We ultimately hope that this simulation advances our understanding of the different types of turbulence on Earth and in space,” Federrath says.

“Next we’d like to add magnetic fields, chemistry and cooling to a simulation of this size, in order to learn more about the processes taking place when stars form.”