Orbital perturbation

An orbital perturbation is a change in an object's idealized orbit caused by forces or effects omitted from a simplified model. Perturbations can alter orbital position, shape, orientation, or timing.

Two-body problem: A model of two bodies interacting only through their mutual gravitational attraction. Perturbations are departures from this idealized baseline.
Keplerian orbit: An elliptical orbit described by Kepler's laws for a body moving under an inverse-square central force. It is the unperturbed orbit against which deviations are measured.
Orbit determination: The estimation of an object's orbit from observations of its position and motion. Observed deviations help estimate both the orbit and unmodeled forces.
Mercury's perihelion precession: The gradual rotation of Mercury's closest-approach direction around the Sun. Its unexplained Newtonian residual became a successful test of general relativity.
General relativity: A theory of gravitation in which matter and energy curve spacetime and bodies follow its geometry. Relativistic corrections perturb orbits beyond Newtonian gravitational predictions.
Gravitational perturbation: An orbital change caused by gravitational forces beyond the central body's two-body attraction. Other bodies and nonspherical mass distributions alter the reference orbit.
Orbital elements: A set of parameters that specifies an orbit's size, shape, orientation, and the body's position. Perturbations are commonly expressed as changes in these parameters.
Orbit propagation: The calculation of an object's future or past trajectory from an initial state and force model. Reliable predictions require accounting for relevant perturbations.
Lagrange point: A location in a rotating two-body system where gravitational and centrifugal effects permit a body's relative position to remain fixed. Nearby orbits are shaped by the competing gravity of two primary bodies.
N-body problem: The problem of predicting the motions of multiple bodies interacting through gravity. It replaces the isolated two-body baseline with explicit mutual interactions.

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