How Do You Calculate the Mass of a Star in Orbit?

[contlee]

Homework Statement

Star A is in a circular orbit of radius R around point P. The period of the star is T. Determine the mass of the Star

Homework Equations

I do not know how to find the mass of the orbiting body. I found the centripetal acceleration which equaled GM/R^2. I could find the mass of P, but not the orbiting body

The Attempt at a Solution

I said that V=2piR/T. then that GM=4pi^2R^3/T^2. But that only gives me the mass of the body the star is orbiting around... Right?

 

[diazona]

I think you're right, at least if you assume that the other body is much more massive than the star itself. Then again, if the other body is much lighter than the star, the mass you find is pretty close to the mass of the star. But the problem doesn't say anything about the other body, so I'm not sure what the intent is.

I'll bring this to the attention of other homework helpers and perhaps one of them will have some insight.