Center of Mass: The point at which the entire mass of an object or a system can be considered to be concentrated, where the object's or system's gravitational pull is centered.
Gravitational Force:The attractive force between any two objects with mass, which is proportional to the masses and inversely proportional to the square of the distance between them.
Binary System: A system of two objects, such as two stars or a star and a planet, that orbit around a common center of mass.