ASTR 1P02 Lecture Notes - Lecture 6: Triple-Alpha Process, Main Sequence, Red Giant
9 Apr 2016
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Document Summary
The onset of he-fusion into 12^c is called the helium-flash. The energy released per single he-fusion reacion is smaller than the energy released per single. The overall fusion rate of he must be higher than the h-fusion during the main sequence stage, and the he is fused much quicker (in about 100 million years) The amount of energy released ater the he-lash is so large that it heats up the core and it expands. As a result of the expansion the edge of the core cools down. This causes the temperature of the h-fusing shell to drop and the fusion in it stops. The removal of this important source of energy causes the pressure to drop. The surface gets closer to the energy producing core and it heats up. This makes the colour change from orange/red to yellow. Eventually all of the 4^he in the core is fused into 12^c.
