life cycle of star

• • stars start as a cloud of dust and gas called a nebula
  • the force of gravity pulls the dust and gas together to form prostar
  • the star gets denser, so the temperature rises, so more particles collide
  • this causes nuclear fusion, the hydrogen nuclei forms a helium nuclei
  • large amounts of energy are given out, and a star is born
• • the star enters the main sequence of its life cycle
  • the star remains stable becuase the gravitational force inwards and forces as a result of fusion reactions outwards are equal
  • stars bigger than the Sun will undergo different processes than stars the same size as the Sun
• • stars the same size as the Sun will swell into a red giant because the hydrogen in the nuclei starts to run out
  • the star becomes red because the surface cools
  • the star will then become unstable and will collapse to become a white dwarf - hot, solid core
  • the star will then cool to become a black dwarf
  • the star becomes a black dwarf when energy emitted is not at a significant amount
• • stars bigger than the Sun will form a red super giant after the main sequence
  • more fusion will occur and the star will explode into a supernova
  • the supernova collapses into a dense core called a neutron star
  • if the star is large enough, it will become a black hole
• • fusion processes in stars produce all natural occuring elements
  • fusion forms elements as heavy as iron
  • the explosion in a supernova forms elements heavier than iron
  • the explosion ejects the elements into the universe to form new planets and stars