Synodic period. astronomy. Synodic period, the time required for a body within the solar system, such as a planet, the Moon, or an artificial Earth satellite, to return to the same or approximately the same position relative to the Sun as seen by an observer on the Earth. The synodic period of an astronomical body is the time interval between its successive conjunctions with the Sun. It is also equal to the time period between the successive apparitions of that body, with the exception?...
