ASTRON 1010 Lecture Notes - Lecture 20: Cno Cycle, Red Supergiant Star, Low Mass
Document Summary
There are two known ways that stars fuse hydrogen to helium in their occurs. The first in the proton-proton chain which occurs in low mass stars. The second in the cno cycle which occurs in higher mass stars: one nucleus goes to become carbon, nitrogen, and oxygen isotopes through a number of transformations in an endless loop. High mass main sequence stars fuse h to he at a higher rate using carbon, nitrogen, and oxygen as catalysts. A greater core temperature enables h nuclei to overcome greater repulsion and fuse h to he in this different process. The cno cycle plays a role in stellar fusion beginning a about 15 million degrees k but is not efficient. At a higher temperature it dominates fusion in the core of a more massive star. High core temperatures in high mass stars allow helium to fuse with heavier elements.
