ASTR 1P02 Lecture Notes - Lecture 5: Red Giant, Main Sequence
8 Apr 2016
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Document Summary
The final stages in the life of a sun-like star. Eventually all of the hydrogen in the core is fused into helium (in about 4. 5-5 billion years) The mass of the sun is not high enough to ignite the he core. He-core contracts under its gravity and heats up: The temperature of contracing he-core is very high and the rate of hydrogen fusion in the shell is very high. It is higher than the rate of fusion in the h-core during the main sequence stage. The higher rate of energy producion results in high gas pressure, which pushes out the top layers and the star expands. As a result the surface temperature drops because the surface is at a greater distance from the energy producing region. The surface temperature drops and its colour changes to orange-red. Our sun is in the irst red giant stage.
