AST-0009 Lecture Notes - Lecture 9: White Dwarf, Mass Transfer, Binary Star
12 Mar 2016
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From reading quiz #12: an accretion disk is a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole. Bright o-type stars live very short lives (~10 million years) Very small stars live a long time (~100 billions of years) Sun: total of about 10 billion years (half of its age) The more massive a star, the faster it goes though its main sequence phase. Stars spend most of their life cycles on the main sequence. Main sequence stars are in hydrostatic equilibrium because nuclear fusion is turning hydrogen into helium and producing enough outward pressure to balance gravitational collapse. 90% of stars are found on the main sequence. 90% of the whole life of all stars is spent on the main sequence. What happens when the hydrogen runs out: stars leave the main sequence. System becomes out of balance (outward pressure less than gravitational pull)
