380 Part IV Stars 13.1 White Dwarfs • What is a white dwarf? A white dwarf is the core left over from a low-mass star, sup-ported against the crush of gravity by electron degeneracy pressure A white dwarf typically has the mass of the Sun compressed into a size no larger than Earth. No white dwarf can have a mass greater than • What can happen to a white dwarf in a close binary system? A white dwarf in a close binary system can acquire hydrogen from its compan-ion through an accretion disk that swirls toward the white dwarf’s surface. As hydrogen builds up on the white dwarf’s surface, it may begin nuclear fusion and cause a nova that, for a few weeks, may shine as brightly as 100,000 Suns. In extreme cases, accretion may continue until the white dwarf’s mass ex-ceeds the white dwarf limit of at which point it will explode as a white dwarf supernova . 13.2 Neutron Stars • What is a neutron star? A neutron star is the ball of neutrons created by the collapse of
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This note was uploaded on 08/16/2011 for the course AST 2002 taught by Professor Britt during the Spring '08 term at University of Central Florida.