Earth trojan

The orbit of 2010 TK7, the first Earth trojan to be discovered (left). Lagrangian points L₄ and L₅. Lines around the blue triangles represent tadpole orbits (right)

An Earth trojan is an asteroid that orbits the Sun in the vicinity of the Earth–Sun Lagrangian points L₄ (leading 60°) or L₅ (trailing 60°), thus having an orbit similar to Earth's. Only two Earth trojans have so far been discovered. The name "trojan" was first used in 1906 for the Jupiter trojans, the asteroids that were observed near the Lagrangian points of Jupiter's orbit.