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Celestial mechanics is the application of mechanics to celestial objects, such as stars, planets, moons, and galaxies. Mechanics, the branch of physics dealing with forces and motion, consists of dynamics, the study of forces and resulting motions, e.g., orbits; statics, the study of forces in the absence of motion, e.g., why the material in the center of an astronomical object (such as the Moon) resists further compression, maintaining the body's current size; and kinematics, the study of motions of objects without regard to the forces that cause it. (Conceptually, a system's dynamics is best worked out after its kinematics has been established.)
For example, Kepler's laws, which describe orbits (Keplerian orbit) fall under the heading of kinematics, whereas Newton's laws, which describe how forces bring about orbits, fall under dynamics. Celestial mechanics, as "mechanics focused on astronomical phenomena", includes some focus on the dynamics of orbiting bodies, and has developed techniques of determining long-term (secular) changes, i.e., perturbation theory.