rotation period
(of a celestial object) time that it takes to complete one revolution around its axis of rotation relative to the background stars
AI overview
A rotation period is how long it takes for a celestial object, like a planet or star, to spin once on its axis when measured against the fixed background of distant stars. Knowing an object's rotation period helps astronomers understand its physical properties and behavior in space.
AI-generated from the Wikipedia summary — may contain errors.
Article
Earth's rotation imaged by Deep Space Climate Observatory, with axis tilt
In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space). The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day.