This is Question 17 from USAAAO Practice Round 2015. The answer is D. It would be best if someone can detail out the workings.
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 an inclination of 90 degrees.
- a. 0.5
- b. 1
- c. 2
- d. 4
- e. 8
What I got so far:
- Distance to system: 2pc (6.171e16 m)
- Minimum separation: 5.98e11 m
- Maximum separation: 5.38e12 m
- Relative semimajor axis: 2.99e12 m (20AU)
- Combined mass: 125 solar masses