Small star life cycle

• Main sequence star [1]

  • hydrogen nuclei are fused together to form helium
  • this releases energy as heat and light
• Red giant [2]

  • eventually all the hydrogen fuel runs out
  • the star cools and expands, becoming a red giant
  • the star then starts to fuse together helium nuclei to release energy
• White dwarf [3]

  • as the helium runs out, the outward forces reduce in size and the star collapses inwards
  • this causes a temperature increase
  • white dwarf is formed, which is the hot core of the star
• Black dwarf [4]

  • when the white dwarf completely cools, it becomes a black dwarf
  • a black dwarf does not emit any light or heat