Sky science
Synodic Period
Direct answer
Synodic Period: A Synodic Period is the interval between repeated alignments of two orbiting bodies as seen from a chosen observer.
It measures the recurrence of an apparent configuration.
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At a glance
- Found in
- Astronomy & Skywatching
- Related
- Orbital Period, Sidereal Period, Periapsis, Apoapsis
It measures the recurrence of an apparent configuration.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.
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The story behind Synodic Period
Synodic cycles were fundamental to early planetary and lunar calendars.
A one-minute story
The Wandering Stars
How the moving planets were watched, named and found, and what a transit is.
Why Synodic Period matters
Synodic Period explains intervals between oppositions, conjunctions, or like lunar phases.
Synodic Period in practice: an example
Mars returns to opposition on a synodic schedule longer than one Earth year.
Where readings of Synodic Period go wrong
A synodic period is not the body’s period around its primary.
Sources and editorial method
Research references used for this entry include:
- NASA Science: Orbits and Kepler’s Laws - NASA explanation of orbital ellipses, orbital periods, and Kepler’s laws of planetary motion.
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Last updated
- 2026-09-26
Compare sidereal and synodic cycles
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More in Astronomy & Skywatching
- Angular Separation
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- Descending Orbital Node
- Gravitational Lensing
- Local Meridian
- Orbital Perturbation
- Quasar
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Common questions
What is a Synodic Period?
A Synodic Period is the interval between repeated alignments of two orbiting bodies as seen from a chosen observer.
What do people get wrong about a Synodic Period?
A synodic period is not the body’s period around its primary.
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