White Dwarf Stars
Evolution to white dwarf
All stars with M < 2 Msun will eventually become white dwarfs. Most stars with 2 Msun < M < 10 Msun will probably wind up as white dwarfs. We have some uncertainty as to what happens for high mass stars.
Take a 2 Msun star
Stages:
1. Red Giant -- He burning in core -- Mass Loss
2. Contracting, heating up -- carbon burning?
3. Planetary nebula -- star ejects more material
4. Runs out of nuclear fuel -- contracts becomes a subdwarf
Lasts ~1012 s ~105 years
5. Stops contracting -- just cools at same radius
What is holding it up?
Electron Degeneracy
Radius gets smaller and smaller -- density gets hgher and higher
What stops it?
Try to put too many electrons in a limited space, each electron needs its own quantum state.
Stops where 
Then it just sits there and cools
R ~ 0.01 Rsun ~ 7*108 cm
L ~ 0.01 Lsun = sAT4
Surface gravity is 104 times that of the sun ~ 108 cm s-2
Magnetic fiels: B ~X 1-100 Mgauss
Made of Carbon or heavier elements
Very high conductivity
Observation
Sirius B
40 Eri B
Procyon B
Nomenclature
DA H lines
DB HeI lines
DO HeII lines
DC continuous
DF CaII lines
DG CaII and FeI lines
C2 bands at l 4670, 5140
Gravitational Redshift
Measure mass dynamically
Measure R from sT4
Know 
Therefore the shift = 1 angstrom
First verification of general relativity