Co-orbital configuration

A co-orbital configuration is an arrangement in which two or more bodies orbit the same central body with the same or nearly the same orbital period. Its members can occupy distinct orbital paths or share a path while remaining separated through gravitational dynamics.

Trojan asteroid: An asteroid that shares a planet’s orbit near one of the stable Lagrange points ahead of or behind it. Trojan asteroids exemplify co-orbitals held near stable points in a planet’s orbit.
Jupiter trojans: Asteroids gathered near Jupiter’s leading and trailing triangular Lagrange points. They are the largest familiar population of co-orbitals in the Solar System.
Joseph-Louis Lagrange: An Italian-French mathematician and astronomer whose work established major foundations of analytical mechanics. His analysis identified the equilibrium points that explain where some co-orbitals can remain.
Mean-motion resonance: An orbital resonance in which bodies’ periods have a ratio close to small integers, not necessarily equal. Most mean-motion resonances involve different periods; co-orbitals have a 1:1 period relationship.
Janus and Epimetheus: Two Saturnian moons that periodically exchange their relative orbital positions without colliding. Their horseshoe-shaped paths produce a striking orbital swap within a shared orbital region.
Saturnian trojans: Small bodies that share Saturn’s orbit near its triangular Lagrange points. Their sparse population contrasts with the extensive Trojan swarms of Jupiter.
Three-body problem: The problem of predicting the motion of three mutually gravitating bodies from their initial conditions. Co-orbital stability is a special question within this classic gravitational problem.
Satellite: A natural or artificial object that orbits a planet or another body. A co-orbital companion shares the central body’s orbit rather than orbiting the planet as a moon does.
Lagrange point: A location in a two-body system where gravitational and centrifugal effects allow a small object to remain in a stable relative position. The triangular Lagrange points support stable co-orbital arrangements such as Trojan populations.
Earth trojans: Asteroids that librate near the leading or trailing triangular Lagrange points of Earth’s orbit. They demonstrate that co-orbital populations also occur on Earth’s orbit.

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