# Mass of stars?

1. Mar 26, 2009

### fball558

mass of stars???

1. The problem statement, all variables and given/known data

About half of the visible "stars" are actually binary star systems, two stars that orbit each other with no other objects nearby. Consider the motion of the center of mass of a binary star system. For a particular binary star system, telescopic observations repeated over many years show that one of the stars (whose unknown mass we'll call M1) has a circular orbit with radius R1 = 8 E 11 m, while the other star (whose unknown mass we'll call M2) has a circular orbit of radius R2 = 11 E 11 m about the same point. Make a sketch of the orbits, and show the positions of the two stars on these orbits at some instant. Label the two stars as to which is which, and label their orbital radii. Indicate on your sketch the location of the center of mass of the system. (Do this on paper; you will not be asked to turn it in. )(c) This double star system is observed to complete one revolution in 48 years. What are the masses of the two stars?

3. The attempt at a solution

i have no idea where to start. i asked 2 of my under grad TA's and they did not know how to do it so though i would come here.
i assumed that the orbits were perfect circles and them found circumference and divided by 48 years. i converted this to m/s and that should be the velocity.
V1 = 3318.44
V2 = 4562.85

#### Attached Files:

• ###### binary_star_orbit.gif
File size:
3.1 KB
Views:
54
2. Mar 27, 2009

### tiny-tim

Hi fball558!

erm … neither you nor the TAs are reading the question

it clearly states:
sooo … another diagram?