Turbulence at astronomical scale.
A slice through the turbulent gas in the world’s highest-resolution simulation of turbulence. Credit: Federrath et. al, Nature Astronomy.

This was originally published via the ANU newsroom.

A new study by an international team of researchers has used computer power to map the so-called "sonic scale", showing the key role turbulence plays in star formation.   

The sonic scale marks the transition from supersonic turbulence, which is faster than the speed of sound, to subsonic turbulence, which is slower than the speed of sound. Gas below the sonic scale may collapse to form stars.

Their simulation is the biggest ever of its kind and could help answer a major question in astrophysics - when and how do stars form in interstellar gas clouds.     

According to lead researcher, Associate Professor Christoph Federrath from The Australian National University (ANU), turbulence is a key ingredient for star formation.

"Turbulence controls the pace of star formation, stirring up gas and slowing down the action of gravity," he said.

"Without turbulence stars form a hundred times quicker than observed.

"While the turbulence itself is supersonic - or faster than the speed of sound - star formation is actually very slow. This is because of the turbulence slowing down star formation, such that only about one sun per year is formed in the whole of the Milky Way. 

"On the other hand, turbulence also triggers the formation of stars on scales below the so-called 'sonic scale'.

The research team are now looking at expanding their study.

"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," Associate Professor Federrath said.

"This will be extremely challenging, as it would take even more memory, space, and computing power. Such a simulation would just fit on Australia's new supercomputer 'Gadi' at the National Computational Infrastructure."  

The research team included scientists from the University of Heidelberg and the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences and Humanities in Germany.

The study has been published in the journal Nature Astronomy.