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Core Helium Double Shell Burning
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 Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf
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Double Shell Burning Molecular Cloud
Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf 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
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Core Helium- Double-Shell Burning
75. Double Shell Burning Name Core Helium- Burning Double Shell- Burning Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Hydrogen Helium Carbon/Oxygen
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Double Shell Burning Molecular Cloud Protostar Main Sequence Red Giant
Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Double Shell-Burning Core Helium-Burning Star moves up and right on H-R diagram
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Giant Stages – Mass Dependence
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf For stars from 0.5 to 3 MSun, 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
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Giant Stages – Mass Dependence
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf
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Giant Stages – Mass Dependence
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Core Helium-Burning
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Giant Stages – Mass Dependence
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Core Helium Burning Double Shell-Burning
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Mass Loss Molecular Cloud
Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf 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
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Dying Stages – Low Mass Stars
Planetary Nebula Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf As the outer layers are lost, inner layers gradually revealed We see the inside of the star Until nearly the end, the inside is unaffected Still burning fuels at the same rate Q. 76: Planetary Nebula on H-R diagram
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Planetary Nebula on H-R Diagram
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Double Shell-Burning Core Helium-Burning Star moves to left on H-R
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Planetary Nebula Q. 77: Planetary Nebula Spectrum
Star becomes so hot it radiates in ultraviolet Visible luminosity goes down Ultraviolet light bumps electrons up in gas surrounding the star Electrons fall back down – make visible light - colors Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Q. 77: Planetary Nebula Spectrum
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Double Shell Burning White Dwarf
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Double Shell- Burning White Dwarf Planetary Nebula Hydrogen Helium Carbon/Oxygen
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Planetary Nebulae Abell 39
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Planetary Nebulae Ring NGC 6751
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Planetary Nebulae Eskimo Hourglass
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Planetary Nebulae Helix NGC 2440 Dumbbell
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Planetary Nebulae Egg
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Planetary Nebulae M2-9 Cat’s Eye Spirograph
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White Dwarfs Q. 78: Why Can’t You Walk Through Walls? Molecular Cloud
Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Burnt out Carbon/Oxygen core Gradually cools and fades Q. 78: Why Can’t You Walk Through Walls?
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Degeneracy Pressure Q. 79: White Dwarf on H-R diagram
Quantum mechanics Certain types of particles: can’t have two of same type in same place Electrons, neutrons, protons When you push them together, you get pressure Greatest for electrons P n5/3/m It is independent of temperature As white dwarf cools, no change in size White dwarf has constant radius, falling temperature Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Q. 79: White Dwarf on H-R diagram
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White Dwarfs Molecular Cloud Protostar Main Sequence Red Giant
Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Double Shell-Burning Core Helium-Burning Star moves to right and down on H-R
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White Dwarf Size and Mass
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf Stars have lost mass Sun will end as about 0.6 MSun 8 MSun will end as about 1.4 MSun The more massive they are, the smaller they are Very dense! Very small! (Earth sized) Maximum mass - Chandrasekhar mass is 1.4 MSun. Any star starting with > 8 MSun cannot end as a white dwarf
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White Dwarf Size and Mass
Molecular Cloud Protostar Main Sequence Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf
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Initial vs. Final Size Molecular Cloud Protostar Main Sequence
Red Giant Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf
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White Dwarf Size Molecular Cloud Protostar Main Sequence Red Giant
Core Helium-Burning Double Shell-Burning Planetary Nebula White Dwarf
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H-R tracks for White Dwarfs
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Summary of Stages: < 8 Solar Masses
Double Shell-Burning Core Helium-Burning
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Summary of Stages: < 8 Solar Masses
Stage Core Activity Size Surface Temp. Molecular Cloud (not a star) Huge Protostar Hydrogen Large Cool Main Sequence Hydrogen burning Small Hot Red Giant Helium ash Large Cool Core Helium-Burning Helium burning Medium Hot Double Shell-Burning Carbon/Oxygen ash Large Cool Planetary Nebula (not a star) Huge White Dwarf Dead C/O core Tiny Hot
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