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| the object is a protostar, no fusion taking place. It is still condensing under the influence of gravity |
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| in the core of the star hydrogen fusion takes place to form helium. The star spends almost all of its lifetime on the man sequence |
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| all the hydrogen in the core has turned into helium and core fusion has ceased. The helium core collapses under influence of gravity and becomes very hot. Hydrogen fusion takes place in a shell around core |
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| the helium core is compressed to become degenerate gas and an explosive beginning to helium fusion occurs here |
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| helium fusion taking place in core to form carbon via the tripe alpha process |
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| all helium in the core has been turned into carbon and core fusion ceases. Helium fusion shell is formed around the hot core causing the star to undergo another expansion and become a supergiant. |
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| formation of a planetary nebula |
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| the outer parts of star escape into interstellar space forming the planetary nebula and eventually leaving behind the carbon core |
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| the outer part of the star has dispersed into interstellar space. The remaining stellar core is now a white dwarf, anf is almost all carbon. It is about the size of Earth, very dense, and is initially very hot. |
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| nova explosion on a neutron star |
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| will leave nothing behind |
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| Why are variable stars important? |
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| distance indicators theory of stellar evolution predicts their existence |
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| light comes from excited atoms |
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| emits light by reflecting light from a nearby star |
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| dust specks in nebula reflecting light |
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| stars appear redder than they actually are |
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| caused by IM preferentially scattering blue light |
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| stars appear dimmer than the should |
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| IM absorbs some of the starlight |
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| em radiation emitted by cold neutral H atoms |
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| electron also rotates on it axis |
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| Stage 1 of Star Formation: interstellar cloud |
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| Stage 1 of Star Formation: interstellar cloud |
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| Stage 2 of Star Formation: collapsing cloud fragment |
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| about 100 times the size of Solar System |
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| initially doesn't heat much because radiation escapes |
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| Stage 2 of Star Formation: collapsing cloud fragment |
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| Stage 3 of Star Formation: fragmentation ceases |
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| roughly size of the solar system |
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| inner part of cloud opaque and heats up a lot |
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| Stage 3 of Star Formation: fragmentation ceases |
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| when fragmentation ceases the inner part becomes a |
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| Helmholtz contraction phase |
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| Stage 4 of Star Formation: protostar-- |
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| prestellar object hot enough to emit IR, but not hot enough for fusion |
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| Stage 4 of Star Formation: protostar |
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| Stage 5 of Star Formation: protostellar evolution |
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| Stage 5 of Star Formation: protostellar evolution |
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| Stage 6 of Star Formation: newborn star |
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| core temp. reaches 10 million K, hot enough to start H fusion |
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| surface a bit cooler than the Sun |
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| Stage 6 of Star Formation: newborn star |
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| Stage 7 of Star Formation: The main sequence |
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| central density about 10^32 |
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| central temp= 15 million K |
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| Stage 7 of Star Formation: The main sequence |
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| stars has arrived along the_____during stage 7 of star formation: the main sequence |
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| zero age main sequence (ZAMS) |
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