17
Motion in the
HR Diagram
•During
H core burning (main
sequence)
–L
increases slowly as He accumulates in the core (and TCore increases)
•During
H shell burning
–At
first R increases, T decreases
–L
then increases slowly as more He accumulates in core (and TCore increases)
–Eventually
He ignites in the core
•During
He core, H shell burning
–Moving
some of E generation back into core shrinks size (and so raises TSurface)
–Eventually
He in core runs out
leaving a C, O core inside the He region
leaving a C, O core inside the He region
–Core
contracts and heats up till He ignites in shell outside C, O core
•During
He shell, H shell burning
–At
first R increases, TSurface decreases
–L
increases as more C,O accumulate and TCore continues to increase
From our text: Horizons, by Seeds