AST201H1 Lecture Notes - Lecture 11: Thermostat, Crab Nebula, Energy Economics
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Ast201: the lifecycle of a 1 solar mass star (chp 17. 1- 17. 2, part 18. 1) Note: low mass stars never get hot enough to fuse carbon into heavier elements in their cores. More massive white dwarfs are smaller in size than less massive ones bc it"s greater gravity can compress its matter to a much greater density. White dwarfs are so called bc: they are both very hot & very small. 0 billion years 10% helium, 90% hydrogen. 5 billion years (now) about half of the core has been converted from hydrogen to helium. Hydrogen shell burning is so intense that it floods the outer layers of the sun with more energy than they used to receive. The sun expands enormously (subgiant/red giant) (part of the slides) Eventually, when the density is high enough, the helium core will ignite! (and the hydrogen shell is still burning too) This will be about 100 million years after leaving the main sequence.