SCI 102 Lecture Notes - Lecture 11: Triple-Alpha Process, Red Giant, Neutrino
13 Apr 2016
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1h + 1h -> 2h + e+ + v (deuterium, positron, neutrino) 2h + 1h -> 3he + y (helium isotope, radiation burst) 3he + 3he -> 4he + 1h + 1h (helium, hydrogen: masses on left will always be greater than masses on right, will be fill in the blanks on a test. This is the luminosity (energy per second) observed for our sun (a typical star) Luminosity = l = 4 pi r2 sigma t4. Star fuses hydrogen nuclei into helium nuclei deep in its core via p-p chain. Core temperature must be at least 10 x 106k = 10 million k. Massive stars: greater core densities, greater core pressures. Faster rate of hydrogen fusion -> shorter main sequence lifetime of only a few million years. Average, normal stars (like our sun) will fuse hydrogen over a lifetime of several billion years. Massive stars only live for a few million years. Normal stars live for billions of years.
