# Equation for Solid Planet Structure

1. Jan 15, 2007

### Helios

I'm looking for an radial equation to find the pressure or density of the interior of a moon or rock planet. It would involve Young's modulus or Poisson's ratio or something like. Any help?

2. Jan 15, 2007

### Chris Hillman

Well, you should probably start with something more basic: the equation of hydrostatic equilibrium. This is relevant to models in which you model a planet or star as a ball of fluid, but also to models in which you model it as an (isotropic, inhomogeneous) elastic medium. I take it you are looking for a Newtonian model? There are many books on Newtonian models of stellar structure, also many books on geophysics.

3. Jan 16, 2007

### Helios

There are books on geophysics? Really? Your reply is kind of a downer. I've solved hydrostatic eq'ns for spheres and I'm looking for a next thing to do.

4. Jan 20, 2007

### Obs

Hi Helios!

Maybe this one is what you are looking for: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1980LPSC...11.1999A&amp;data_type=PDF_HIGH&amp;type=PRINTER&amp;filetype=.pdf [Broken]
I'm not so good at math and physics, so I don't really understand everything in the text. If you can use the formulas in the text to find density (and temperature), please tell me how!

Last edited by a moderator: May 2, 2017
5. Jan 20, 2007

### Chris Hillman

The next thing after fluid balls in hydrostatic equilibrium?

Hi, Helios,

Sorry if I underestimated your previous experience. Should I infer from your handle that you are particularly interested in stellar interiors? Would adding rotation whet your appetite? If so, if you know about McLaurin spheroids, I suppose the obvious next question is: have you studied Chandrasekhar, Selected Papers, esp. Vols 1, 4? That should keep you happy for a while!

Last edited: Jan 20, 2007
6. Jan 28, 2007

### Helios

Hi Chris. I have Chandra's book "Stellar Interiors" and that's it. Out of it I'm trying to understand his explanation of composite polytropes. I don't get it and there are no examples.
Anyway I'm looking for a solid planet equation that might resemble Emden's eq'n.