Sidereal and Synodic Periods

The Sidereal Period of an object is the time it takes to make a complete circuit of the celestial sphere with 

respect to the fixed stars. The Synodic Period is the time required to make a circuit of the celestial sphere 

with respect to the Sun - which is also moving eastward among the stars. The synodic period is always 

greater than the sidereal period, the difference being due to the apparent motion of the Sun. The sidereal 

period of the Moon is the time it takes to go once around the Earth; the sidereal period of a planet is the 

time it takes to go once around the Sun. i.e., its orbital period.

Worked example on planets:

Reference 

Nmsu kurt

Nmsu nicole

Nao jp