AS101 Lecture Notes - Lecture 13: Mass Transfer, Cosmic Distance Ladder, Roche Lobe
Document Summary
Interesing fact: if stars didn"t die, we would not exist. Once they exhaust their hydrogen reserves, stars enter sage of their life cycle. Stars spend about 10% of their total lifeime in the giant stage. As the star fuses hydrogen, helium accumulates in the core, diminishing the star"s ability to generate nuclear energy: to fuse into heavier elements, helium requires temperatures exceeding 100 million kelvin. The core of helium ash contracts and grow hoter, triggering fusion of hydrogen in the outer shell: stars move toward the upper right on the h-r diagram. Once the helium ash core reaches 100 million kelvin, it stars helium into carbon. Giant star: large, cool, highly luminous star in the upper right of the h-r diagram, typically 10-100 imes the diameter of the sun. Nuclear fusion in 2 locaions- hydrogen fusion in the shell and helium fusion in the core. Carbon and oxygen ash accumulate in the inert core.
