- #1

- 148

- 0

## Main Question or Discussion Point

**Gravitational Potential Energy Problem**

I have this problem and it has been bugging me

The problem (if i recall correctly) went like this:

Ive got an earth like object ( m = 6E24 kg) that will fall 1 A.U = 1.5E11 m

towards a neutron star with a radius of 1E4 m. At this point it will presumably break up and form an accretion disc around the neutron star.

The goal is to calculate roughly the resulting temperature of the accretion disc.

so i started by assuming the virial theorem applies

Kinetic energy = 1/2 * Potential energy

so,

3/2 kT = G M m / 2 r (1)

I am trying to solve for Temperature but I do not know the mass of the neutron star M. I know m = 6E24 and i know r = 1.5E11 m

how do I solve for M?

well heres what i did

M = density * volume

I took a typical density of a neutron star, say, 1E18 kg/m^3

I know volume = 4/3 Pi r^3 and r = 1E4 m

I get mass of neutron star = 4E30 kg

plug this into (1)

I find the temperature to be 10^*(56) kelvin???

thats ginormous! where did i go wrong? or perhaps that was the point of the equation?

blumfeld0

Last edited: