sidereal year

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sidereal year (plural sidereal years)

  1. The orbital period of the Earth; a measure of the time it takes for the Sun to return to the same position with respect to the stars of the celestial sphere. A sidereal year is about 20.4 minutes longer than the tropical year (which is what is kept stable by the Gregorian calendar) due to precession of the equinoxes.
  2. The time it takes for any astronomical object in orbit around a central start to orbit that star, with respect to distant stars.


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