[Stellar Structure] White Dwarves

[ajclarke]

Homework Statement

Have to calculate the Electron-Degeneracy Pressure as a fraction of the total pressure in a white dwarf. Given Density and Temperature.

Homework Equations

$$(\frac{1}{5m_{e}}) (\frac{3h^3}{8 \pi})^{2/3} (\frac{\rho}{\mu_{e}M_{H}})^{5/3}$$

The Attempt at a Solution

I have calculated the Electron-Degeneracy Pressure as:

$$3.383 \times 10^{61} \textrm{Pa}$$

Now I need to calculate the Thermal Pressure using the density and temperature so I can find this fraction but I can't for the life of me think how to do it.

Cheers

 

[ajclarke]

Shameless bump, could really use some help with this.

I have tried a bit more myself. Using:

$$P=\frac{\rho k T}{\mu} = \frac{1.3807 /times 10^{-23} \times 3 \times 10^6 \times 2 \times 10^7 \times 3}{4}=6.213 \times 10^{-10}$$

Using values given above, and taking mu as being 4/3 for pure helium. However this seems very very small, given that atm P = 100KPa (approx)

ALso if I then finish the question of the fractional degenerate pressure, being such a large number gives it as 1.

Thanks in advance.

 

[ajclarke]

Last ditch attempt before It has to be handed in.