1. The problem statement, all variables and given/known data Three identical stars, each with mass m, form the verticies of an equilateral triangle with side length d and rotate in a circular orbit due to their mutual gravitation. What is the period τ of their rotation? I set up the FBD for each star and am now trying to figure out what to do from there. I know how to get period into the equation from circular motion, but is that all there is to it? The FBD gives different equations for each mass so when I solve I get different periods for each star. What should I be doing here? Force equations Star at bottom left point: x: Fcosθ+F = max y: Fsinθ = may Star at bottom right: x: -(Fcosθ+F) = max y: Fsinθ = may Star at top: y: -2F = may (or should this be -2Fcos(θ/2)?) x: forces cancel to 0 If you draw an equilateral triangle you will see what I'm talking about and then how I oriented my axes around the stars.