Lagrange Points

The Lagrange points in the restricted three-body problem mark positions where the combined gravitational pull of the two large masses equals precisely the centripetal force required for a particle of negligible mass to rotate with them around the center of gravity. There are five such points; three are stable, placed on the line that connects the masses, and each of the other two forms an equilateral triangle with the masses. The dashed curves show zero velocity curves. Several satellites have been placed at these points.