suppose that a binary star system consists of two stars of equal mass. they are observed to be separated by 360 million km and to take 5.0 earth years to orbit about a point midway between them. what is the mass of each? P. 135 "Physics: Principles With Applications" Fourth Edition. Giancoli. 1995. after much discussion with my dad, and working it many times, we get 1.11x10^30 kg as the mass. the answer in the back of the book is 5.5x10^29 kg. we noticed it is half of our answer, but the thought is that the book is missprinted. help?