SCI238 Lecture : L15.docx
9 Jul 2013
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When the supernova explodes it expels heavy elements into space, and produces new elements (heavier than iron) in the ejecta. This is the only known process that makes these elements. sequence of mass, pressure support limits, density, radius all are: small, dense, no fusion. White dwarf (wd) -> neutron star (ns) -> black hole => White dwarfs the exposed core of a star that has died and shed its outer layers in a planetary nebula. It is quite hot when it first forms, because it was the inside of a star, but it slowly cools with time. No internal energy source -> white dwarfs cool. > black dwarf: its size will never change, because its electron degeneracy pressure will forever keep it stable against the crush of gravity. if they were gaseous they would contract as the gas pressure would decrease. But, white dwarfs are supported by electron degeneracy pressure. More massive star evolves first to giant or supergiant.
