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Stars and stellar Evolution

A typical star is a ball of hot gases sustained in a steady state by the balance between gravitational collapse and the expansive pressure from internal fusion. However, students should understand that stars, like the Sun, are not static, but pass through a number of stages between being formed and "dying." They can be environments of intense mechanical and magneto-dynamic activity. Different types of stars have different spectra, based on their composition, temperatures, and age, and all these factors change throughout the lifetime of each star. The mass and size of a star help to determine its life cycle, and how it will end--as a white dwarf, a neutron star or a stellar black hole.   Stellar life cycles become apparent when many stars can be mapped on a Hertzsprung-Russell, or H-R diagram.