ASTR 101 1st Edition Lecture 28 Outline of Last Lecture I. Low-mass starsII. Life stages of low-mass starsOutline of Current Lecture I. Life track of a sun-like star,II. Life stages of high-mass stars,III. High-mass stars make elements necessary for lifeCurrent LectureI. Life track of a Sun-like Stara. Our Sun is a low-mass star. Once hydrogen is completely exhausted, it will evolve from the main sequence. It will eventually become a white dwarf. II. Life stages of a high-mass star:a. The core in a high-mass star is even hotter than in a low-mass star. There is only proton-proton collision in low-mass, and now we have hydrogen atoms colliding withhelium using carbon, nitrogen, and oxygen as catalysts. A greater core temperature enabled H nuclei to overcome greater repulsion. b. This is done through the CNO cycle. The net effect is still converting 4 protons into 1 helium. c. Life stages of high-mass are similar to that of low-mass stars, but high-mass stars evolve very fast compared to a low-mass stari. Hydrogen core fusion (in the main sequence)ii. Hydrogen shell fusion (as a supergiant)iii. Helium core fusion (also as a supergiant)iv. This time we will have other elements burning on the shell as well. II. High-mass stars make elements necessary for lifea. The force of gravity in a high-mass star keeps its carbon core so hot that degeneracy pressure is not a factor. Once helium fusion stops, gravitational contraction of carboncore continues until the core reaches 600 million K, which allows carbon to be fused into other elementsb. Gravitational equilibrium is temporarily restored by carbon fusion, carbon fusion continues until it is depleted once again, and still more elements are able to be formed. This struggle between the star and gravity will eventually result in the formation of new elements. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c. Multiple shell burning: near the end of the star's life, its inside contains layers of different each fusing a different element… iron piles up in the silicone-fusing core toward the very end. Core temperatures in stars with greater than 8MSun allow the fusion of elements as heavy as iron. Iron is unique-- it is not possible to generate nuclear energy from Iron, which has the lowest mass per nuclear particle. d. Iron appears to be the most stable element, and elements heavier than iron are not produced in stars. e. There is a higher abundance of elements with even numbers of protonsf.How does a high-mass star die? --Through a Supernova