Life cycle of star

• Nebula


  A large cloud of dust and gas in space

  
• Protostar


  Formed from the core of a nebula after it collapses under its own gravity

  
• Nuclear fusion (stars)


  Begins when the core of a protostar becomes hot and dense enough for fusion to start

  
• Main sequence star


  A star that is in equilibrium and remains in this phase for most of its lifetime

  
• Equilibrium (stars)


  When the gravitational collapse of a star is balanced by the expansion due to the energy released by fusion

  
• The Sun


  A relatively small, main sequence star that is roughly in the middle of its life cycle

  
• Red giant


  Formed when a star about the same size as the Sun runs out of hydrogen so larger nuclei form and the star expands

  
• White dwarf


  Formed when the nuclear reactions in a red giant stop and it starts to contract due to its own pull of gravity

  
• Black dwarf


  Formed when a white dwarf cools until it no longer emits any radiation

  
• Red super giant


  Formed when star much larger than the Sun runs out of hydrogen so larger nuclei form and the star expands

  
• Supernova


  Occurs when a red super giant expands until it explodes, throwing hot gas into space

  
• Neutron star or black hole

  Left behind after a supernova and depends on the mass of the star at the start of its life

  
• Forming elements in stars

  All the naturally occurring elements are produced by fusion reactions in stars
• How the lighter elements (up to iron) form

  Formed in main sequence stars when the hydrogen runs out, so helium nuclei start to fuse etc
• How the heavier elements (heavier than iron) form


  Formed when a supernova explodes and are thrown out into the universe