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1. (captured rotation) The rotation of a natural satellite about its primary in which the period of rotation of the satellite is equal to its orbital period. The same hemisphere thus always faces the primary. The Moon is in synchronous rotation, although libration allows slightly more than one hemisphere to be seen from Earth. There are good dynamical reasons for satellites fairly close to their planet being locked in synchronous rotation. See tidal force.
2. (synchronism) A situation in a close binary star in which the rotation period of a star is equal to the binary's orbital period (for circular orbits).
synchronous rotation[′siŋ·krə·nəs rō′tā·shən]
The rotation of a planet or satellite whose period is equal to its orbital period.