AST 341 Lecture Notes - Lecture 17: Photon, Stellar Evolution, Triple-Alpha Process

• School: Stony Brook University
• Department: Astronomy
• Course: AST 341
• Professor: Rosalba Perna

Document Summary

After discussing stars during their lifetime, we will now turn to a discussion of their end states. Here we consider low-mass stars, i. e. those which were born with masses m 7m . Towards the end of their life, these stars have c-o core surrounded by a helium burning shell, in turn surrounded by a hydrogen burning shell, which becomes thinner and thinner. The c-o core"s evolutionary course and its consequences are similar to the helium core"s. Devoid of energy sources, the core contracts and heats up; as a result, the envelope expands and cools, and convection sets in again throughout it. The hydrogen burning shell gets soon extinguished and the burning products (mainly helium and nitrogen) get mixed up int he envelope. The star expands and becomes redder, resuming its climb on the giant branched in the h-r diagram (which had been interrupted by the core helium burning episode).