August 1 , Lecture 10, AST201H1
Best learn about the life cycle of people by bringing home the crowds on the street.
More massive stars take less time to form!
0 billion years- 10% He, 90% H
Sun starts to shrink release gravitational potential energy. Excess goes to heating
Release gravitational potential energy ignite hydrogen shell burning.
Hydrogen shell burning is so intense that it floods the outer layers of the Sun with
more energy than they receive. The sun expands dramatically. Also turns red. The
sun while on main sequence, the sun as a red giant.
This will be about 100 million years after leaving the MS.
Helium fusion turns on very suddenly. Helium flash.
“lives again!” fusing helium to make