Stars form out of clouds of dust
- The particles in the clouds gather together due to gravity
- The clouds then merge together to form a 'protostar' (star soon to be born)
- The protostar begins to become denser, getting hotter
- Once it has become hot enough the nuclei of hydrogen and other light elements fuse together
- Energy is released during this process so the core gets hotter, this results in shining
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The stars radiate energy due to the hydrogen nuclei inside them fusing together.
- The nuclear fusion will continue for millions of years until the hydrogen supply runs out
- The force of gravity that makes a star contract is balanced by te outward pressure of radiation from its core
- These forces stay in balance until all of the hydrogen nuclei have been fused together
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Stars die when they run out of hydrogen nuclei to fuse together
- The star swells, cools and turns red - beoming a 'red giant'
- During this stage helium and other light elements fuse together to make heavier ones
- Once all of the light elements have been used up fusion stops. The star collapses on itself, it heats up and turns from red to yellow to white - becoming a 'white dwarf'
- This is much denser an smaller than it was
- After a while it fades out and goes cold
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Supernova and Black Holes
The death of bigger stars is much more spectacular
- The collapse continues past the 'white dwarf'
- It reverses into a cataclysmic explosion known as a 'supernova'
- The explosion compresss the core of the star into a 'neutron star'
- This is an extremely dense object composed of neutrons
- If it is big enoug it becomes a 'black hole'
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