What are Lagrangian orbits?
A tristar system appears to be clearly an unstable system at first glance, since minor gravity disturbances in the system will cause one of the orbiting stars to advance on the other leading top collision and ultimate merger of the two orbiting stars.
However, there are two points in such an orbit where there is comparative stability and safely from any such catastrophic collisions. These points are called the Lagrangian points. Located 600 ahead or behind the other orbiting body, the Lagrangian points form a perfect equilateral triangle with the central star. The stars located at Lagrangian points in such an orbital configuration would then be said to be in a Lagrangian orbit. A Lagrangian orbit can apply to planets also e.g. the Lagrangian points of Jupiter containing the ‘Trojan’ asteroids.