The chain of events that connects the accretion disk around a young star to a planetary system such as the Solar System
begins with random motions of the gas within the protoplanetary disk. These motions push the smaller grains of solid material back and forth past larger grains; and as this happens, the smaller grains stick to the larger grains. The “sticking” process among smaller grains is due to the same static electricity that causes dust and hair to cling