PHYS 183 Chapter Notes - Chapter 13: Helium Flash, Reaction Rate, Triple-Alpha Process
15 Mar 2017
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13. 1 (lecture 19): 4 phases of stellar life, formation and pre-main sequence, main sequence, post main sequence, (cid:498)death(cid:499, stars form from gas in very cold (10-30 k) molecular clouds. There is lots of dust in these clouds that obscures most of the light, only infrared light emerges. Because they are very cold so molecules can form and remain stable (b): density perturbations form the core for star formation. When it becomes very dense nuclear reactions begin. It is a relatively short phase, massive stars reach the main sequence the fastest. Answer: brown dwarf (a) reactions to begin: zero age main sequence (zams) is where stars of the same chemical composition start. As the stars age they make the main sequence line thicker. 13. 2 and 13. 3 (lectures 20 and 21): a star"s fate depends critically on its mass. Low mass stars (less than 2 solar masses) become white dwarfs.
