Trojan asteroids, or “Trojans,” move in orbits with the same average distance from the Sun as a planet. This may seem as a precarious state to be in, as eventually the asteroid either hits the planets or is flung, by the planet’s gravity, on an entirely different orbit.
But solar and planetary gravity combine in such a way as to create dynamical “safe havens” 60 degrees in front and behind the planet’s orbital phase. The special significance of these, as well as three other similar locations in the so-called three-body problem, was worked out by
18th century French Mathematician Joseph-Louis Lagrange. In his honor, they are nowadays referred to as the Lagrange points. The point leading the planet is referred to as L4; that trailing the planet as L5.
Read more at: Phys.org