Calculate the time it takes for a celestial body to return to the same position relative to the Sun as seen from Earth.
Last updated: March 2026 | By Summacalculator
Earth: 365.25 days
Mars: 686.98, Jupiter: 4332.59, Saturn: 10759.22
The synodic period is the time it takes for a celestial object to reappear at the same point in the sky relative to the Sun, as observed from Earth. For example, the time between two successive oppositions of Mars or two successive full moons.
This differs from the sidereal period, which is the time it takes for an object to complete one full orbit around the Sun relative to the fixed stars. Because Earth is also moving in its orbit, the synodic period is always different from the sidereal period.
Because Earth moves faster than Mars. After Earth completes one orbit, it must 'catch up' to Mars again before they are in the same relative position to the Sun.
The Moon's synodic period (the time between full moons) is about 29.53 days, while its sidereal period (orbit around Earth) is 27.32 days.
Yes. The formula works for any two bodies orbiting the same central object. For Venus, P₂ is shorter than P₁ (Earth).
If two bodies have the same orbital period, they will never change their relative position, and the synodic period becomes infinite.
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