دورهی ِ هماگمی
Fr.: période synodique
1) For planets, the mean interval of time between successive
→ conjunctions of two planets, as observed from the Earth.
For → inferior planets (Venus and Mercury):
1/P = 1/E + 1/S.
For → superior planets (Mars, Jupiter, etc.):
1/P = 1/E - 1/S,
where P = → sidereal period of a planet, E = synodic period of
the Earth, and S = synodic period of the planet. For example, the synodic period of Jupiter,
from the sidereal period of Jupiter (P), 11.856 years, via 1/11.856 = 1/1.0 - 1/S, is
2) For satellites, the mean interval between successive conjunctions of a satellite with
the Sun, as observed from the satellite's → primary.
→ synodic; → period.