Kepler orbit

Summary

A Kepler orbit is the path of a body that moves under the inverse-square gravity of a single point mass and feels no other force. It is a conic section with the attracting centre at a focus: an ellipse, a parabola or a hyperbola. In the degenerate case it is a radial line. It is the exact solution of the two-body problem and the starting point of all orbit calculations. See the definition.