The Life Cycle of Stars

• Protostar


  Cloud of dust and gas that forms a star due to gravity
• Star formation


  1. Cloud of dust and gas forms

  2. Gravity pulls dust and gas together

  3. Protostar forms
• Main Sequence Star


  Star in a long stable period where nuclear fusion balances gravity
• Main Sequence Star


  1. Hydrogen undergoes nuclear fusion to form helium

  2. Outward pressure from fusion balances inward gravity

  3. Star remains stable for billions of years
• Red Giant


  Larger star that swells and cools as hydrogen runs out, then fuses helium and heavier elements
• Red Super Giant


  Larger version of a Red Giant
• Red Giant/Super Giant


  1. Hydrogen runs out

  2. Star swells and cools

  3. Fusion of helium and heavier elements occurs
• White Dwarf


  Hot, dense, solid core left behind when a small-to-medium star ejects its outer layers
• Black Dwarf


  White dwarf that no longer emits a significant amount of energy
• Neutron Star


  Very dense core left behind after a supernova explosion
• Black Hole


  Super dense point in space that not even light can escape from, formed from the core of a massive star after a supernova
• Supernova


  1. Massive star undergoes more fusion and expansion/contraction

  2. Explodes, ejecting elements heavier than iron into space
• Stars and their life cycles produce and distribute all naturally occurring elements