
The rotation period of an astronomical object is the time that it takes to complete one revolution around its axis of rotation relative to the background stars. It differs from the planet`s solar day, which includes an extra fractional rotation needed to accommodate the portion of the planet`s orbital period during one day. ==Measuring rotation=.....
Found on
http://en.wikipedia.org/wiki/Rotation_period

The time taken for one complete turn through 360°. It may refer either to an object's axial period or its orbital period.
Found on
http://www.daviddarling.info/encyclopedia/R/rotation_period.html
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