This is the process and the evolution of a Solar Mass Star:

  1. The star’s core is made up of helium and surrounded by a hydrogen shell.
  2. As hydrogen burns faster, it comes to an end and is not sufficient for helium to start burning.
  3. The radiactive pressure goes outwards to resist gravitational collapse. In the outer regions temperature increases and hydrogen fusion can occur.
  4. The core continues to collapse and the outer regions keep increasing their temperature and luminosity. Now everything exerts a pressure.
  5. Pressure makes the outer layers to expand, they cool down and the star becomes redder. After millios of years the hydrogen shell runs out of fuel.
  6. The star turns into a red giant and is seen as a nebula leaving a core behind.
  7. The core has half of the mass of a star and will eventually cool down.
  8. The atoms are packed and the star turns into a white dwarf.