P2- 7.5- the life history of a star

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  • Created by: Grace
  • Created on: 06-05-13 11:41
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  • 7.5- The life history of a star
    • Gravitational forces pull clouds of dust and gas together to form a protostar
    • the protostar becomes denser and the nuclei of hydrogen stoms and other light elements start to fuse together. Energy is released in the process so the core gets hotter and brighter
    • Stars radiate engery because of hydrogen fusion in the core.
      • this stage can go one for billions of years untill the star runs out of hydrogen nuclei.
        • the star is sable becuase the inward forceof gravity is balanced by the outward force of raditation from the core
          • this is called a main sequence star
            • this stage can go one for billions of years untill the star runs out of hydrogen nuclei.
              • the star is sable becuase the inward forceof gravity is balanced by the outward force of raditation from the core
                • this is called a main sequence star
      • eventually the star will run out of hydrogen, swells, cools down and turns red. what happens next in the life cycle of the star depends on its size
      • A star similar in size to our sun ( low mass) is now a red giant
        • helium nad other light elements fuse to form heaviern elements
          • Fusion stops and the star will contract to form a white dwar.
            • eventually no more light is emitted and the star becomes a black dwarf.
      • A star much larger than the sun will swell to become a red supergiant which continues to collapse
        • eventually the star expodes in a supernova.
          • the outer layers are thrown into space
          • the core is left as a neutron star
            • if this is massive enough it becomes a black hole.
              • the gravitaional field of a black hole is so strong not even light can escape it.
      • low mass star: protostar- main sequence- red giant- white dwarf- black dwarf
      • high mass star: protostar- main sequence star- red supergiant- supernova- black hole (if big enough

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