Trojan asteroid

A Trojan asteroid shares a planet’s orbit while remaining near its L4 or L5 Lagrange point, roughly 60 degrees ahead of or behind the planet.

Lagrange point: A location in a rotating two-body system where gravitational and centrifugal effects allow a smaller object to remain in a stable relative position. Trojan asteroids cluster around the L4 and L5 points of a planet–Sun system.
Jupiter trojans: Asteroids that share Jupiter’s orbit near its leading and trailing Lagrange points. They form the largest and most studied Trojan population in the Solar System.
Jupiter trojan color bimodality: The division of Jupiter’s Trojans into two broad groups with different visible colors and surface properties. Their distinct colors may record different source regions or histories.
Quasi-satellite: A co-orbital object that appears to circle its planet from the planet’s perspective but actually orbits the Sun. Unlike a Trojan, it follows a looping relative path rather than librating around L4 or L5.
1:1 orbital resonance: An orbital relationship in which two bodies complete one revolution in the same time. A Trojan and its planet share an orbital period while occupying different positions along the orbit.
Neptune trojans: Asteroids that share Neptune’s orbit near its L4 or L5 point. Their distant orbits provide a contrasting population to Jupiter’s Trojans.
Nice model: A Solar System formation model in which giant planets migrated and destabilized a primordial population of small bodies. Planetary migration in this model can capture and redistribute Trojan asteroids.
Horseshoe orbit: A co-orbital trajectory in which an object’s relative motion traces a horseshoe-shaped path around a planet’s orbit. It shares a planet’s orbital period but spans a much wider range of relative positions than a Trojan.
Restricted three-body problem: A model of two massive bodies and a third, negligible-mass body moving under their gravity. It describes the dynamics that make Trojan regions possible.
Earth trojan: An asteroid that shares Earth’s orbit near one of its stable Lagrange regions. Earth has a known Trojan, showing that the phenomenon is not limited to giant planets.

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