The life cycle of a star consists of 5 main stages: 1. Protostars form from huge clouds of gas that collapse under gravity. 2. Main sequence stars like our Sun fuse hydrogen for billions of years. 3. Red giants expand and their outer layers cool as hydrogen runs out. 4. White dwarfs form as red giants collapse under gravity into dense remnants. 5. Black dwarfs are the final remains that cool for eternity, emitting no light.