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Gravity must decrease due to less effective mass when going inside the object but also must increase with depth inside the star due to its higher density. Is there a model or formula approximating gravity calculations along the radius (from center to surface) of the stars?

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For example, I've found a relation for Earth's gravity variation with depth on Wikipedia. I hope that stars do have similar approximations. I don't know how the density distribution will vary with depth (or is it uniform?). – Tariq Nov 16 '12 at 10:44

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up vote 3 down vote accepted

You need to know the equation of state for the star's interior. Once you know this you can calculate the density variation with depth and the gravity inside the star.

Google for something like "star equation of state" to find lots of articles on the subject, but note that it's exceedingly complicated because there are so many factors at work. This is the sort of article you'll find: good luck reading it!

Note also that while we can use models to calculate equations of state, the results are only as good as the models. It's hard to know how good our models are when all we can see is the surface of the star.

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However strange it may sounds at first, white dwarfs (at least those well below the Chandrasekhar limit of 1.4 solar masses) are probably the easiest stars to model - the reason is that you can ignore temperature in the equation of state. – Leos Ondra Nov 15 '12 at 19:01
@John Rennie, thanks for the update and the pdf file. @ Leos Ondra thanks for commenting. – Tariq Nov 16 '12 at 10:08

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