ASTR 114 Lecture Notes - Lecture 17: Triple-Alpha Process, Degenerate Matter, Red Giant
10 Jan 2020
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Document Summary
Mass measurements of ms stars show that the hot stars are much more massive than the cool ones. The mass of a star determines its luminosity and spectral type. Stars form in dark clouds of gas in interstellar space- gas is called interstellar medium. Composition of gas can be determined by spectral lines. Milky way is 70% h, 28% he and 2% heavy elements. Emission lines from molecules in a cloud can prevent a pressure buildup by converting thermal energy into infrared and radio photons that escape the cloud. Fragmentation of a cloud: random motion of sections of cloud cause it to become lumpy -each lump can become a star. Trapping of thermal energy: contraction packs molecules together, photons can"t escape, energy and pressure builds up, contraction slows down and center of cloud becomes a protostar. Collisions between particles in the cloud cause it to flatten into a disk.
