Points in the orbital plane of two massive objects circling about their common centre of gravity where a particle of negligible mass can remain in equilibrium. There are five such points for two bodies in circular orbits around each other, but three are unstable to small perturbations. The other two, at points 60° either side of the less massive body and in the same orbit, are stable. The Trojan asteroids, which share the orbit of Jupiter, are examples of masses trapped at the two stable Lagrangian points in an orbit. See also: Roche lobe.