lifecycle of a star

• general start:

  1. cloud of dust and gas (nebula) is pulled together due to gravitational attraction, becoming a protostar
  2. the protostar is pulled together by gravity and the particles in the protostar collide more frequently
  3. more energy is transferred from the GPE store to the thermal energy store, so temperature increases
  4. the temperature gets warm enough for nuclear fusion of hydrogen nuclei, forming helium nuclei and releasing lots of energy
  5. the protostar becomes a main sequence star. The inward force of gravity is balanced with the outwards force created by high pressure. Star is stable.
• stars about the size of the sun (after general start):

  6. over time, the hydrogen gets used up through fusion and so there are a larger proportion of larger nuclei, meaning the star grows to become a red giant

  7. the nuclear reactions stop as reactants are used up. The star contracts due to gravity and it becomes a white dwarf

  8. once all the thermal energy from the white dwarf has been been radiated away, the white dwarf cools down to form a black dwarf
• stars larger than the sun (after general start):

  6. becomes a red super star as the nuclear fuel starts to run out, and there's a greater proportion of larger nuclei, meaning the star grows to form a red super giant

  7. the core of the star will collapse to form a supernova, causing a massive explosion in which elements heavier than iron are produced and distributed throughout the universe

  8. at the centre of the explosion, a neutron star will form

  9. or for particularly massive stars, the centre will continue to collapse under the force of gravity, forming a black hole