 These are the two observable quantities needed to calculate the binary mass function.The observed object of which the radial velocity can be measured is taken to be object 1 in this article, its unseen companion is object 2.Let formula_3 and formula_4 be the stellar masses, with formula_5 the total mass of the binary system, formula_6 and formula_7 the orbital velocities, and formula_8 and formula_9 the distances of the objects to the center of mass.