what is a sidereal year
Because, for all intents and purposes, the sky is âfixedâ, a sidereal day is when the earth rotates 360Â°. A sidereal day is 23 hours 56 minutes and 4.09 seconds long. A sidereal year is the time it takes for the sun to return to the same position with respect to the stars. Due to the precession of the equinoxes the sidereal year is about 20 minutes longer than the tropical year. The tropical year is the interval at which seasons repeat and is the basis for the calendar year.