AST 10G Lecture Notes - Lecture 8: Planetary Nebula, Degenerate Matter, White Dwarf
Document Summary
Double shell burning ends with a pulse(s) that eject the outer h & he into space as planetary nebula. No longer fusing h he doesn"t quite qualify as star. Fusion progresses no further in a low-mass star because the core temp never grows hot enough for fusion of heavier elements (some he fuses to carbon to make oxygen) Degeneracy pressure supports the white dwarf against gravity. Electrons having to go into higher energy states, this is what support star . High mass stars make the elements necessary for life. To low-mass stars except that hey occur faster. Greater core temp enables hydrogen nuclei to overcome greater repulsion. High mass main sequence stars fuse h to he at high rate using carbon, nitrogen and oxygen catalysts. High mass stars-have high enough core temp & pressure to fuse heavier elements beyond carbon. They do this by fusing helium nuclei to heavier elements (he capture)