Binary stars move in paths called their orbits.
As we learned in
Binary Star Systems,
the paths of these stars are described by the formula:
for first star 

second star 
mass * distance to center of mass 
= 
mass *
distance. to center of mass 
Important Information:
A line drawn between
two binary stars always goes through the center of mass.
As binary stars move in their
orbits, they are always exactly opposite each other.
Here are some sample orbits that binary stars may move in:
This diagram shows a set of binary stars which
both have circular orbits.
