The gravitational attraction between any two objects is dependent on their combined mass and the distance between them. The gravitational attraction of a massive body is a function of the gravitational constant, and the attraction felt between two separate objects obeys the inverse-square law.
One way of describing the effect of gravity in a two-object system is that the force of gravity is in direct relation to the mass of the objects and in inverse relation to the distance between them. Using Newton's Law of Gravitation, F = G M m / r^2, it is possible to calculate the force between objects. Double the mass of an object, and its gravitational pull doubles. Double the distance between objects, and the attraction between them declines by 75 percent.