Star life cycle

• Life cycle of stars

  1. Big cloud of dust and gas (nebula)

  2. Gravity pulls dust and gas together to form a protostar

  3. Protostar gets bigger and denser

  4. Temperature and pressure increase

  5. Hydrogen nuclei fuse to form helium (nuclear fusion)

  6. Star becomes a main sequence star

  7. Main sequence star has balanced outward and inward pressure

  8. Star runs out of hydrogen

  9. Gravity contracts star into a small ball

  10. Nuclear fusion starts again, forming heavier elements

  11. Small/medium star becomes a red giant

  12. Red giant expels outer layers, leaving a white dwarf

  13. White dwarf cools to become a black dwarf

  14. Massive star becomes a red supergiant

  15. Red supergiant explodes in a supernova

  16. Supernova ejects heavy elements

  17. Massive star condenses into a neutron star or black hole
• Nebula


  Big cloud of dust and gas
• Protostar


  Structure formed as gravity pulls dust and gas together
• Nuclear fusion

  Hydrogen nuclei fuse to form helium, releasing energy
• Main sequence star


  Star with balanced outward and inward pressure
• Red giant


  Star that expels its outer layers, leaving a white dwarf
• White dwarf


  Hot, dense solid core of a red giant
• Black dwarf

  White dwarf that has cooled and no longer emits light
• Red supergiant


  Massive star that explodes in a supernova
• Supernova


  Explosion of a red supergiant, ejecting heavy elements
• Neutron star


  Dense core left behind after a supernova of a large (but not massive) star
• Black hole


  Extremely dense object formed from the collapse of a massive star, with gravity so strong that even light cannot escape