Dying Stages – Low Mass Stars
Planetary Nebula
•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
As the inner layers are revealed, how
does the star move on the H-R diagram?
A) Left
C) Up
E) Left and Up
B) Right D) Down F) Right and Down
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Planetary Nebula on H-R diagram
Double ShellBurning
Core HeliumBurning
•Star moves to left on H-R
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Planetary Nebula
•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
What would the spectrum of a planetary
nebula be like?
A) A dark line spectrum
B) A bright line spectrum
C) A continuous (black body) spectrum
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Double Shell Burning   White Dwarf
Double
ShellWhite
Planetary
Dwarf
Burning
Nebula
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Hydrogen
Helium
Carbon/Oxygen
Planetary Nebulae
Abell 39
Planetary Nebulae
Ring
NGC 6751
Planetary Nebulae
Eskimo
Hourglass
Planetary Nebulae
Helix
NGC 2440
Dumbbell
Planetary Nebulae
Egg
Planetary Nebulae
M2-9
Cat’s
Eye
Spirograph
White Dwarfs
•Burnt out Carbon/Oxygen
core
•Gradually cools and fades
Why can’t two objects be at the same
place at the same time? How come
you can’t walk through walls?
A) Electromagnetic forces
B) Strong nuclear forces
C) Gravitational forces
D) Quantum mechanics
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Degeneracy Pressure
•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 HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
White Dwarfs
Double ShellBurning
Core HeliumBurning
•Star moves to right and down on H-R
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
White Dwarf Size and Mass
•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
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
White Dwarf Size and Mass
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
Initial vs. Final Size
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
White Dwarf Size
•Molecular Cloud
•Protostar
•Main Sequence
•Red Giant
•Core HeliumBurning
•Double ShellBurning
•Planetary Nebula
•White Dwarf
H-R tracks for White Dwarfs
Summary of Stages: < 8 Solar Masses
Double ShellBurning
Core HeliumBurning
Summary of Stages: < 8 Solar Masses
Stage
Molecular Cloud
Protostar
Main Sequence
Red Giant
Core Helium-Burning
Double Shell-Burning
Planetary Nebula
White Dwarf
Core Activity
(not a star)
Hydrogen
Hydrogen burning
Helium ash
Helium burning
Carbon/Oxygen ash
(not a star)
Dead C/O core
Size
Huge
Large
Small
Large
Medium
Large
Huge
Tiny
S. Temp.
Cool
Hot
Cool
Hot
Cool
Hot