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- The orbits are elliptical.
- The Sun is at one of the foci of the ellipse.
- The Orbital Speed is such that a line between planet and Sun sweeps out the same area over any equal time-intervals.
As quoted here, the laws would apply (as a special case) to a circular orbit with constant orbital speed. The laws are generally useful for bodies orbiting around others, yielding very good approximations given some assumptions, among them that the "central" body is by far the most massive, that the bodies are basically spherical, that Gravitational interactions between bodies orbiting the central body are minimal, and that Relativistic Speeds are not involved. Orbits that do not match these laws yield information when analyzed to uncover which assumptions don't hold and to what degree. astrophysics,orbits,kinematics)Referenced by:
Celestial Mechanics Keplerian Disk Kepler Radius |