Stars Lifecycle

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

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

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

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'