Stars like the Sun begin their lives as cold, dense cores of dust and gas that collapse under the influence of gravity until nuclear fusion is ignited. These cores contain hundreds to thousands of solar-masses of material and have gas densities about a thousand times greater than typical interstellar regions (the typical value is about one molecule per cubic centimeter). How the collapse process occurs in these embryos in poorly understood, from the number of stars that form to the factors that determine their ultimate masses, as well as the detailed timescale for stellar birth. Material, for example, might simply fall freely to the center of the core, but in most realistic scenarios the infall is inhibited by pressure from warm gas, turbulent motions, magnetic fields, or some combination of them.
"Far-Infrared Dust Temperatures and Column Densities of the MALT90 Molecular Clump Sample," Andrés E. Guzmán, Patricio Sanhueza, Yanett Contreras, Howard A. Smith, James M. Jackson,Sadia Hoq, and Jill M. Rathborne, ApJ 815, 130, 2015.