This movie depicts the evolution of a gravitationally unstable disk in orbit around a Sun-like young star (not shown). The protoplanetary disk has a mass about 10 percent of the Sun's mass. The disk's inner edge lies at 4 times the Earth-Sun distance (4 AU), while the outer edge extends to 20 AU. Stronger colors indicate greater gas density; black indicates low gas density. Watch as dense clumps come and go in the evolution, becoming denser and denser until they become massive enough to sustain themselves gravitationally.