Their are 2 stars orbiting one another. Their masses are equal. The speed at which they rotate is 220 km/h, and their orbital period is 14.4 days. Find the mass of the Star. 2. Relevant equations 220km/h = 61.1m/s 14.4 days = 51840s V= 2pi(r)/T F=ma F=mv^2/R F= m4pi^2r/T^2 Fg= Gm(star1)m(star2)/r^2 These are all the equations I've been using. So far, using V= 2pi(r)/T I can deduce that the radius of the star is 504111.2m and using V=d/t I THINK I can say that the space between the stars is 3167424m, but Im not sure. I've also tried equating F=mv^2/r with Fg = Gm(star1)^2/r^2, and then found the mass to be 3.616x10^13. I don't think this is right, as my teacher said hint: The mass of the sun is 1.99*10^30 kg. I know I often make stupid math mistakes, but I can't seem to find out where I went wrong... Can anyone help me?