INTEGBI C13 Study Guide - Comprehensive Final Guide: Cosmic Microwave Background, Galaxy Cluster, Cambrian Explosion
28 Nov 2016
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Lecture 10: the life and death of stars. Stars are powered by hydrogen helium fusion for most of their lives. The sun has about a 10 billion year lifetime. Some stars have lifetimes that are greater than the age of the universe. Stellar properties change in time because fusion literally changes what stars are made of. If it weren"t for a stronger greenhouse effect in the past, the earth"s temperature would have been around 25 degrees celsius (45 degrees fahrenheit) colder. The sun"s luminosity increases as more hydrogen fuses into helium. The earth will be incinerated as the sun expands. Gravity wins, core contracts and heats up fusion of heavier elements fusion ends gravity wins, core contracts and heats up. Fusion inexorably proceeds to heavier and heavier elements. The fate of a star depends on its birth mass. White dwarfs and neutron stars do not require high temperatures or fusion for pressure support.
