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## Homework Statement

A double star located at a distance of 10 light years from us. The maximum angle between the stars, as seen from Earth, is 2 arcseconds. (1 arcsecond = 1 / 3600 degrees), we can assume that the stellar orbit is circular and that this angle gives us the real distance between the stars. We observe that the rotation period of the stars is 4 years. What is the sum of stellar masses?

## Homework Equations

Newton's law of universal gravitation:

[tex]F_{G}=G\frac{m_{1}m_{2}}{r^{2}}[/tex]

Centripetal force:

[tex]F_c=\frac{mv^2}{r}[/tex]

Kepler's third law:

[tex]P^{2} \propto a^{3}[/tex]

## The Attempt at a Solution

The stellar orbit is circular, so the gravitational force should be equal to the centripetalforce, but how do I proceed?