life cycle of a star

• Star lifecycle


  1. Cloud of dust and gas (nebula) collapses due to gravity

  2. Protostar forms as temperature rises

  3. Hydrogen nuclei fuse to form helium (nuclear fusion)

  4. Main sequence star stage
• Main sequence star


  • Hydrogen nuclei fuse to form helium
  • Releases a huge amount of energy
  • Can stay in this stage for a very long time
• Lifecycle of a star about the same size as the Sun

  1. Hydrogen runs out

  2. Outward fusion force less than inward gravity force

  3. Star collapses and temperature increases

  4. Helium nuclei fuse to create heavier elements

  5. Star expands to form a red giant

  6. Red giant stops fusing helium

  7. Star shrinks to form a white dwarf

  8. White dwarf cools down to form a black dwarf
• Lifecycle of a much larger star than the Sun

  1. Runs out of hydrogen and leaves main-sequence

  2. Expands into a red supergiant

  3. Helium nuclei fuse to produce heavier elements

  4. Red supergiant stops nuclear fusion

  5. Star explodes in a supernova
• Nuclear fusion cannot make elements heavier than iron
• Supernova


  Explosion of a star where temperature is high enough to produce elements heavier than iron
• Elements heavier than iron are only produced in a supernova
• Remains of a supernova

  • Can form a neutron star (densely packed neutrons)
  • Can form a black hole (extremely strong gravity)
• There will be plenty of questions on the life cycle of stars in the vision workbook