Orbital resonance

Orbital resonance occurs when orbiting bodies have orbital periods in a ratio of small integers, producing recurring alignments and repeated gravitational interactions.

Mean-motion resonance: A resonance in which orbiting bodies complete orbital revolutions in a ratio of small integers. This is the standard form of orbital resonance, linking period ratios to recurring gravitational tugs.
Galilean moons: The four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. Io, Europa, and Ganymede participate in the Solar System's best-known three-body orbital resonance.
Planetary migration: The gradual change in a planet's orbit through interactions with a disk or other bodies. Migration can sweep resonances across small bodies and capture them into new orbital relationships.
Orbital commensurability: A near-integer ratio between orbital periods, whether or not resonant dynamics are present. A period ratio close to a small-integer ratio alone does not establish orbital resonance.
Resonant angle: A combination of orbital longitudes and periapsis directions that may librate rather than circulate in a resonance. Its bounded oscillation distinguishes a genuine resonance from a period ratio that is merely near an integer ratio.
Neptune: The eighth planet from the Sun and the most distant major planet in the Solar System. Neptune's migration helped capture many Kuiper belt objects into resonances.
Nice model: A model of Solar System evolution in which the giant planets migrated and destabilized an early outer system. Its migration history uses resonances to explain the giant planets' later orbital arrangement.
Co-orbital configuration: An arrangement in which two bodies share nearly the same orbital period and similar orbital paths. Co-orbital motion is a special orbital relationship, distinct from the usual separated-orbit resonances.
Libration: An oscillation of an orbital angle around a stable value rather than continuous circulation. Resonant angles often librate, making the repeated orbital geometry dynamically stable.
Plutino: A Kuiper belt object in a 3:2 mean-motion resonance with Neptune. Pluto is the archetypal example of this resonant population.

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