PX158 - I7a - white dwarfs

consists of cores from stars that have finished fusion
pauli's exclusion principle: no two electrons can occupy the same quantum state
the de broglie wavelength gives the mean spacing between the electrons:

λ = \frac{h}{p} = n_{e}^{- \frac{1}{3}}

where, $n_{e} =$ number density of electrons

E_{d} = \frac{p^{2}}{2 m_{e}} = \frac{h^{2} n_{e}^{\frac{2}{3}}}{2 m_{e}}

key features:
- there is no temperature dependence
- $E \propto \frac{1}{m}$ means electrons have much higher degeneracy energy for similar $n$ than protons or neutrons
if a box of degenerate electrons is compressed, $n_{e}$ , and therefore $E_{d}$ would increase
therefore work needs to be performed
*degenerate electrons exert a pressure
this pressure supports white dwarfs
electrons are stripped from the carbon and oxygen nuclei
nuclei provide most of the mass, and electrons, most of the pressure
$R_{W D} \approx R_{\oplus}$ , $M_{W D} \approx 0.6 M_{⊙}$ , and $ρ_{W D} = 10^{9} k g m^{- 3}$
white dwarves have very strong gravitational fields, and can accrete material
they convert accreted mass to radiation (energy) with a $15 %$ efficiency (cf: $H$ -fusion: $0.7 %$ )