Astronomy 1021 Chapter Notes - Chapter 14: Strong Gravity, Energy Star, Observable Universe
16 Dec 2017
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Composition reflects the products of a star"s final fusion stage. Typical white dwarf has the mass of the sun but the size of the earth. More massive white dwarfs are smaller than less massive ones. Electrons move faster the denser the star becomes, making the degeneracy pressure higher, balancing the increased force of gravity. The most massive white dwarfs are therefore the smallest: the white dwarf limit. No white dwarf can have a mass greater than 1. 4msun. The electrons would then be moving faster than the speed of light and that"s not possible. This is known as the white dwarf limit. What can happen to a white dwarf in a close binary system: left alone, a white dwarf will never shine as bright as it once did. Eventually it will cool into a black dwarf": accretion disks. In a close binary system, a white dwarf can gradually gain mass if its companion is a main-sequence star or a giant star.
