Star formation. Image 4 of 6. Computer model of a 2.6-light year diameter sphere of interstellar gas 171,000 years after it began collapsing under its own gravity, a process that causes star formation. Brighter areas have a greater gas density where new stars and brown dwarfs (white) form. The gas ball has a mass 500 times that of the Sun. This model used a supercomputer at the United Kingdom Astrophysical Fluid Facility (UKAFF) at the University of Leicester, UK. Simulations such as this increase understanding of the chaotic processes of star formation, and the likelihood of the formation of planetary systems around new stars. For a sequence showing star formation over 209,000 years, see images R590/117-122.