# Homework Help: Eddington luminosity for star made out of protons

1. Mar 30, 2010

### gamer3999

Imagine that a star could be composed entirely of protons so that Thomson scattering by protons dominated the stellar opacity. How luminous, in $$L_{\odot}$$, would the star have to be to blow itself apart by radiation pressure?

I know that the luminosity has to be greater than the eddington luminosity so that radiation pressure is greater that gravity.

The equation I have for scattering for protons is $$\sigma_{T} = \frac{1*C^2}{6\pi}* (\frac{p^2}{(m_{p} * c^2)})^2$$

This gives me $$3.90 * 10^{-35} meters^2$$

The eddington luminosity equation is then $$L = \frac{4\pi*G*(m_{p}*C*mass of star)}{\sigma_{T}}$$

The problem is that I wasn't given a mass or radius for the star, so I'm stuck.

Last edited: Mar 30, 2010