2. Main Sequence  Red Giant At the center, Hydrogen is gone – there is only Helium “ash” As more Helium accumulates, gravity pulls the core together – it shrinks and heats up Hydrogen continues to burn in a layer around the center High temperature – it burns fast Luminosity rises This dumps lots of heat into the outer layer It expands and cools Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Giant Stages – Low Mass Stars

3. Hydrogen Helium Main Sequence  Red Giant Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Main SequenceRed Giant

4. Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Star moves up and right on H-R diagram Core Helium- Burning Double Shell- Burning

5. Red Giant The star is incredibly bright and incredibly large Goodbye Mercury It is using up fuel faster than ever It evolves fast 200 Myr for Sun The core keeps getting more massive, more compressed, and hotter It accelerates faster and faster Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf

6. An Aside: Some Nomenclature Issues Astronomers use different names for the same thing My old tests, and occasional diagrams, use alternate names: New Names:Old Names: Core Helium-BurningHorizontal Branch Double Shell-BurningAsymptotic Branch Massive Star SupernovaType II Supernova White Dwarf SupernovaType I Supernova

7. More Nuclear Physics There are other processes besides Hydrogen burning At 100 million K, three Heliums can join to make carbon plus a little energy 3He  C + Energy With a little higher temperature, they can add one more to make oxygen C + He  O + Energy These processes produce far less energy than hydrogen burning

8. Red Giant  Core Helium Burning Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf At 100 million K, the helium core in a red giant star ignites Suddenly for light stars (< 3 M Sun ) Gradually for heavy stars (> 3 M Sun ) New heat source in core It expands and cools Hydrogen, still burning in a shell, burns more slowly now Less heat going into hydrogen envelope Hydrogen envelope shrinks and heats up Star moves down and left on H-R diagram

9. Red Giant  Core Helium Burning Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Hydrogen Helium Carbon/Oxygen Red Giant Core Helium- Burning

10. Core Helium Burning Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Star gets hotter and dimmer Core Helium- Burning Double Shell- Burning

11. Core Helium  Double Shell Burning Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf The star is burning Helium to Oxygen and Carbon It doesn’t produce much energy – Helium gets used up fast Eventually, Helium is completely used up and we have a Carbon/Oxygen core left 50 Myr for the Sun The star enters Double Shell-Burning

12. Double Shell Burning The Core consists of Carbon/Oxygen ash It grows more massive over time Heat is leaking out of it It gets smaller and hotter Helium and Hydrogen burning accelerate Lots of energy dumped in outer layers Star gets big, cool, and luminous Bye bye Venus and maybe Earth Star gets brighter than ever Up and to the right again on H-R diagram Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf

13. Core Helium- Burning Double Shell- Burning Core Helium-  Double-Shell Burning Hydrogen Helium Carbon/Oxygen Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf

14. Double Shell Burning Star moves up and right on H-R diagram Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Core Helium- Burning Double Shell- Burning

15. Giant Stages – Mass dependance For stars from 0.5 to 3 M Sun, it is qualitatively the same Heavy stars do everything faster For heavier stars, some details are different Higher temperature and lower density Core isn’t so compact No dramatic increase in luminosity Motion on the H-R diagram is mostly horizontal Stars get bigger and cooler, not brighter Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf

16. Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Giant Stages – Mass dependance

17. Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Giant Stages – Mass Dependence Core Helium-Burning

18. Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf Giant Stages – Mass Dependence Double Shell-Burning Core Helium Burning

19. Mass Loss During Red Giant and especially Double Shell-Burning stage, star is huge and luminous Gravity is weak at the surface Dust particles form on surface These absorb light very efficiently Light pressure begins pushing surface away Like solar wind, but much stronger Star begins to quickly lose substantial mass The inside is hardly affected, for a while Hydrogen  Helium  Carbon/Oxygen Molecular Cloud Protostar Main Sequence Red Giant Core Helium- Burning Double Shell- Burning Planetary Nebula White Dwarf