The orbital period is the time taken for a given object to make one complete orbit around another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.The sidereal period is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference.
The synodic period is the temporal interval that it takes for an object to reappear at the same point in relation to two or more other objects. The synodic period is the time that elapses between two successive conjunctions with the Sun–Earth line in the same linear order. The synodic period differs from the sidereal period due to the Earth’s orbiting around the Sun.
When two bodies orbit a third body in different orbits, and thus different orbital periods, their respective, synodic period can be found.
|Psyn||synodic period (sec)|
|P1||sidereal period of 1st body around the 3rd (P1<P2) (sec)|
|P2||sidereal period of 2nd body around the 3rd (P1<P2) (sec)|