USAAAO — 2015 Practice Round

In a nearby star system, two stars are seen to orbit each other every 8 years. At their closest, the stars are 2” apart. At their furthest, they are 18” apart. If a parallax of 0.5” is observed for the star system, what is its combined mass in solar masses? Assume the orbit is viewed face-on, so the separations are true separations. [Answer choices and the orientation wording updated to correct typos in the original exam.]