Life Cycle of a Star

• how do stars form

  dust and gas cloud is present in a galaxy - the gravitational attraction draws them together - as particles get closer, cloud becomes more concentrated - temperature and pressure increase as particles get pushed closer - eventually, pressure gets so high the particles fuse
• what happens after the particles fuse

  fusion occurs as the light nuclei fuse together to form helium nuclei, creates a large amount of energy, the release opposes the collapsing of the cloud due to gravity - eventually an equilibrium forms, where the energy released balances the pressure of gravitational collapse - a star has now formed
• when do stars start to die

  when they run out of gas to fuse - meaning it is not in equilibrium, so it collapses
• what happens if a massive star starts to die

  star will collaps, increasing pressure and temperature of the core - heavier elements can fuse

  once fusion has happened, too massive to be stable, the star collapses, rebounds on its centre and produces a supernova - a neutron star or black hole remains
• what happens if a normal-sized star starts to die

  (the same process) less fusion occurs as there's less fuel to fuse, the star collapses and produces a planetary nebula (lower scale supernova) - white dwarf remains
• life cycle of a star (the size of the sun)

  protostar - main sequence star - red giant star - white dwarf - black dwarf
• life cycle of a star (much bigger than the sun)

  protostar - main sequence star - red super giant star - supernova - black hole / neutron star
• how do all stars begin

  a cloud of dust and gas (nebula) becomes a protostar
• what happens when a star is a main sequence star

  gravitational attraction collapses the star - radiation pressure expands the star - both forces are balanced