Astrophysicists Reveal New Explanation for Star Formation in Molecular Clouds

How do stars form? Scientists have long speculated exactly how these bright objects form in our universe. Now, we're learning a bit more about star birth. Scientists have provided an explanation for the origin of three observed correlations between various properties of molecular clouds in the Milky Way galaxy known as Larson's Laws.

Larson's Laws describe the observation-based relationships of the structure and supersonic internal motions of molecular clouds, which is where stars form. Yet researchers have long wondered about the internal dynamics of these clouds. In order to learn more about them, the researchers took recent observational measurements and data from six simulations of the interstellar medium, including effects of self-gravity, turbulence, magnetic field and multiphase thermodynamics. Using a supercomputer, they incorporated the data to create simulations.

"After decades of inconclusive debate about the interpretation of the correlations among molecular cloud properties that I published in 1981, it's gratifying to see that my original idea that they reflect a hierarchy of supersonic turbulent motions is well supported by these detailed new simulations showing that the debated complicating effects of gravity, magnetic fields, and multiphase structure do not fundamentally alter the basic picture of a turbulent cascade," said Richard Larson, responding to the new findings by the UC San Diego researchers, in a news release.

The findings essentially support a turbulent interpretation of Larson's relations. In fact, there are no three independent Larson laws. Instead, all three correlations are due to the same underlying physics--the properties of supersonic turbulence.

"This paper is essentially the culmination of seven years of research, aided by the use of large-scale supercomputer simulations conducted at SDSC and elsewhere," said Alexei Kritsuk, one of the researchers, in a news release. "Molecular clouds are the birth sites for stars, so this paper relates also to the theory of star formation."

The findings are important for better understanding star formation. More specifically, it reveals the underlying physics of this formation. This, in turn, could allow astronomers to understand a little bit more about galaxy formation in our universe.

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.