The Evolution of Stars Stars form dense clouds of gas and dust.
Gravity condenses part of the cloud into a warm, red protostar.
As the core of the prostar grows hotter, it glows a bright red. The prostar spins and is flattened into a disk. The infant star remains at the core, and planets may form from rings in the disk. Contraction heats the core until nuclear fusion of hydrogen into heluim begins. The new star becomes a main sequence star and shines for billions of years.