AST Test 4 Post main sequences
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Created by:
crussell6809 on November 15, 2011
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10 terms
Terms | Definitions |
|---|---|
 Post Main Sequence Evolution for Low Mass Stars: Step 1 | All hydrogen in core is converted into helium |
| Post Main Sequence Evolution for Low Mass Stars: Step 2 | With no fusion heat to provide gas pressure, gravity starts to shrink core. The contracting core releases energy that starts H fusion at boundary (=shell) |
| Post Main Sequence Evolution for Low Mass Stars: Step 3 | The H->He shell gives energy to the envelope which drives a tremendous expansion into a "red giant" star |
| Post Main Sequence Evolution for Low Mass Stars: Step 4 | Helium flash drives helium fusion to begin |
| Post Main Sequence Evolution for Low Mass Stars: Step 5 | Core stops shrinking because now there's a gas to support it. Envelope shrinks back to normal |
| Post Main Sequence Evolution for Low Mass Stars: Step 6 | This entire process is repeated when the helium core is changed into carbon. This time the shrinking core makes a helium fusion shell. Heat from this shell drives the envelope to expand and produce a Red Giant a second time |
| Post Main Sequence Evolution for Low Mass Stars: Step 7 | The He is unstable and thermal pulses drive the envelope produces a "planetary Nebula." On the H-R diagram, the star ascends to the red giant region, known as Red Giant Branch |
| Post Main Sequence Evolution for Low Mass Stars: Step 8 | After the Helium Flash, the star "moves" to the HB (Horizontal Branch). Core Helium fusion occurs |
| Post Main Sequence Evolution for Low Mass Stars: Step 9 | The 2nd ascent to the RGB is known as the AGB (Asymptitc Giant Branch) Helium used up in the core |
| Post Main Sequence Evolution for Low Mass Stars: Step 10 | Low mass stars can not get high enough temperature for any new fusion, although core contracts until no longer possible to do |
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