star_stuff_3 - Interstellar polluters pulsations can dredge...

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The evolution of the sun ( a typical low mass star). 1) Deplete H in core 2) Core contracts, heats up, rapid H burning in shell, star expands as red giant. 3) Helium flash 4) Stable core helium fusion, shell H fusion, becomes a horizontal branch star. 5) Core He depleted, double shell burning (He, H), star expands again. Double shell burning After core He depleted, He fuses into C in a shell around the carbon core, and H fuses to He in a shell around the helium layer. Star swells to become an even bigger red giant (radius ~1 AU) Double shell burning is not stable 6) rate of double shell fusion is variable (periodic thermal pulses) and star pulses.
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Unformatted text preview: Interstellar polluters pulsations can dredge up carbon and oxygen from the core, and eject it into the interstellar medium. Stars with carbon rich atmospheres are called carbon stars. The end of fusio n • In a low-mass star, the core temperature never grows hot enough to fuse carbon (some He fuses to C to make O) …left with a hot carbon and oxygen core. Planetary nebulae 7) Pulsations become violet and eject outer layers, producing a planetary nebula Why does a planetary nebula grow? • The ejected layers are excited by radiation from the hot core • Lasts only ~1million yrs....
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This note was uploaded on 04/08/2011 for the course ASTRO 1020 taught by Professor White during the Winter '09 term at UGA.

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