Celestial mechanics is the branch of astronomy that deals with the
motions of celestial objects. Historically celestial mechanics
applies principles of physics (classical mechanics) to astronomical
objects such as stars and planets to produce ephemeris data. As an
astronomical field of study celestial mechanics includes the
sub-fields of orbital mechanics (astrodynamics) which deals with
the orbit of an artificial satellite and lunar theory which deals
with the orbit of the Moon.