If we could observe a planet in orbit around the Sun but very far away, as its distance approached infinity, its synodic period would approach:

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Quizplus · Accepted Answer

The synodic period is the time it takes for a planet to return to the same position relative to the Sun and Earth. At infinite distance, the planet would have an orbital period equal to that of a circular orbit around the Sun at the same distance (per Kepler's third law). Since the planet's orbital period is equal to 1 Earth year, its synodic period would also be 1 year.

If We Could Observe a Planet in Orbit Around the Sun