space

• star life cycle (nebula to main sequence star)

  1. nebula (cloud of dust and gas)
  2. gravity pulls dust and gas together and a protostar is formed
  3. more particles join and it gets bigger so gravity increases which squeezes the protostar. more collisions so temperature and pressure increase. hydrogen fuses to form helium (nuclear fusion) so a main sequence star is formed
• star life cycle (main sequence)

  1. outwards pressure = inwards pressure so the star is stable
  2. the star will begin to run out of hydrogen so gravity takes over and contracts the star into a small ball until very hot and dense
  3. nuclear fusion starts again and the star expands. heavier elements are formed.
• a small medium star will form a red giant

  a really big star forms a red super giant
• red giants

  1. becomes unstable and expels outer layers of dust and gas
  2. hot dense solid core left behind
  3. a white dwarf is formed
  4. it gets cooler and darker and emits its energy
  5. becomes black dwarf as theres not enough energy to emit light
• red super giant

  1. more nuclear fusion so they shine brightly
  2. go through several cycles of expansion and contraction
  3. explode in a supernova forming elements heavier than iron which are ejected
  4. if very big condense into neutron start
  5. if massive it will collapse onto itself and form a black hole