AST 101 Lecture Notes - Lecture 13: Triple-Alpha Process, Stellar Evolution, Low Mass
Document Summary
Lowest temperature = lowest mass = longest main sequence life time. Bigger the mass small the size. As surface temp drops so does its luminosity and its position on the hr. Low mass stars (<10 solar masses) evolve different from high mass stars (>10 solar masses) Decline in core temp causes fusion rate to drop core contracts & heats up. Rise in core temp causes fusion rate to rise core expands and cools down. As the core contracts, h begins fusing to he in a shell around the core. Luminosity increases because core thermostat is broken increasing fusion rate in shell does not stop the core from contracting. Life track for low-mass star after main sequence: Luminosity increasing with time as shell burning & contraction releases more energy. Star stars to get physically larger in response to additional energy. Moves up and to the right on the hr diagram. Eventually, core temperature becomes hot enough to ignite helium fusion.
