ASTRON 1F03 Lecture Notes - Lecture 8: Stellar Evolution, Electron Degeneracy Pressure, Planetary Nebula
12 Mar 2018
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Document Summary
On the main sequence stars are in hydrostatic equilibrium. As h is consume and helium accumulates, the star starts to leave the man sequence, from this point on its evolution depends on its mass. stage 8, subgiant. As the core keeps collapsing h burning in the h burning shell intensi es and the outer layers of the star expand and cool=> redgiant, lower temp but very luminous due to increased size. stage 10, he fusion. As the temperature rises to 100000000 he nuclei start to fuse into. At the same time, the leftover h and he keep burning causing and expansion of the outer layers which now have a very low density=> high density/hot c core+ low density outer layers. => planetary nebula. What keeps the nucleus from collapsing to an in nitely small size? electron degeneracy pressure:arises when electrons become very closely packed. stage 13, white dwarf.
