the life cycle of a star

• Nebula


  A cloud of gas and dust in outer space. If massive enough, these can collapse under gravity to form a protostar.
• Protostar


  A star in the earliest stage of its formation, when it is still gathering mass from the surrounding cloud of gas and dust.
• Main sequence star


  A stable stage in the life cycle of a star. Nuclear fusion occurs, fusing hydrogen nuclei into helium nuclei. There is a balance between the outwards radiation and the force of gravity pulling inwards.
• Red giant star


  A large, cool, luminous red star that is in a late stage of stellar evolution.
• White dwarf


  A small, dense, and extremely hot star that is in the final stage of its life cycle.
• Main sequence star


  A stable stage in the life cycle of a star where nuclear fusion occurs, fusing hydrogen nuclei into helium nuclei. There is a balance between the outwards radiation and the force of gravity pulling inwards.
• Supernova


  The large explosion at the end of a large star's life, which distributes much of the elements formed in the star across space.
• Fusion reactions in a main sequence star

  Hydrogen nuclei fuse together to form helium nuclei
• Neutron star


  A very dense, collapsed star composed almost entirely of neutrons.
• Two hydrogen nuclei fuse to produce a helium nucleus and a neutron
• The Sun is expected to be a main sequence star for billions of years
• Black hole


  A region of space-time from which nothing, not even light, can escape.
• The formation and life cycle of stars

  1. Nebula

  2. Protostar

  3. Main sequence star

  4. Red giant star

  5. White dwarf

  6. Supernova

  7. Neutron star or black hole
• All the naturally occurring elements in the Universe are produced by nuclear fusion reactions in stars
• During the majority of a star's lifetime, hydrogen nuclei fuse together to form helium nuclei
• As the star runs out of hydrogen, other fusion reactions take place forming the nuclei of other elements
• Elements heavier than iron are formed in the supernova explosions of high mass stars
• When the supernova explodes, all the elements produced are thrown out into the Universe
• The heavy elements found on Earth, such as gold, came from material thrown out in previous supernova explosions
• The Big Bang produced hydrogen and helium. All the other elements have been produced by nuclear fusion reactions in stars and supernova explosions