# Degeneracy pressure of a White Dwarf Star

Homework Statement:
A stable white dwarf star has mass m = 10^30 kg and radius R = 8 ×10^8 m. What is the degeneracy pressure of the electron gas in the star?
Relevant Equations:
P = 2πc/3h^3 × P(F)^4 × [1 - {mc/P(F)}^2]
where P(F) = h(3N/8πV)^(1/3)
So far, I am provided with all the required values for calculation, except N.
If N = total number of electrons in star, then using N = mass of star/ mass of an electron should be no problem.
Am I right?

SammyS
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Homework Helper
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Homework Statement:: A stable white dwarf star has mass m = 10^30 kg and radius R = 8 ×10^8 m. What is the degeneracy pressure of the electron gas in the star?
Relevant Equations:: P = 2πc/3h^3 × P(F)^4 × [1 - {mc/P(F)}^2]
where P(F) = h(3N/8πV)^(1/3)

So far, I am provided with all the required values for calculation, except N.
If N = total number of electrons in star, then using N = mass of star/ mass of an electron should be no problem.
Am I right?
That can't be right.

That would work if the white dwarf star were composed entirely of electrons.

berkeman
That can't be right.

That would work if the white dwarf star were composed entirely of electrons.
I think N is given by: N = M/(2×Mass of a proton)

SammyS
Staff Emeritus
Homework Helper
Gold Member
I think N is given by: N = M/(2×Mass of a proton)
That may make sense.

What is the typical composition of a white dwarf star?

Sir usually WDSs are mainly composed of C-12 & O-16.