Astronomy 1021 Lecture Notes - Lecture 3: Triple-Alpha Process, Degenerate Matter, Horizontal Branch
16 Oct 2018
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Document Summary
Star lives is the last chapter of material for this midterm. As a star is generating energy through nuclear fusion, its chemical composition is gradually changing. (transforming hydrogen into helium) Low mass stars on the ms have a slow and steady life. Fusion transforms 4h particles into 1 he particle: since the number of particles drops, the pressure drops and thus the core contracts slightly and heats up. On hr diagram, stars slowly move a little upward as they grow older. After the hydrogen is gone, at some point the hydrogen in the core is completely transformed into helium, and thus there is no more fuel for fusion. The core is now inert (no more fusion) and made of he. No more fusion = no more energy production. Gravity > pressure: gravity starts winning the ght again. Gravity winning = star and core contract. !1: higher temperature hydrogen fusion = faster than regular energy production.
