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A mean solar day is, therefore, nearly 4 minutes longer than a sidereal day. The stars are so far away that Earth's movement along its orbit makes nearly no difference to their apparent direction (except for the nearest stars if measured with extreme accuracy; see parallax ), and so they return to their highest point at the same time each ...
A mean solar day is about 3 minutes 56 seconds longer than a mean sidereal day, or 1 ⁄ 366 more than a mean sidereal day. In astronomy, sidereal time is used to predict when a star will reach its highest point in the sky. For accurate astronomical work on land, it was usual to observe sidereal time rather than solar time to measure mean solar ...
In astronomy, the rotation period or spin period [1] 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 ).
A sidereal day is about 4 minutes less than a solar day of 24 hours (23 hours 56 minutes and 4.09 seconds), or 0.99726968 of a solar day of 24 hours. [7] There are about 366.2422 stellar days in one mean tropical year (one stellar day more than the number of solar days). [8]
This results in culminations occurring every solar day at different times, taking a sidereal year (366.3 days), a year that is one day longer than the solar year, for a culmination to reoccur. Therefore, only once every 366.3 solar days the culmination reoccurs at the same time of a solar day, while reoccurring every sidereal day. [6]
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Thus, the sidereal day is shorter than the stellar day by about 8.4 ms. [37] Both the stellar day and the sidereal day are shorter than the mean solar day by about 3 minutes 56 seconds. This is a result of the Earth turning 1 additional rotation, relative to the celestial reference frame, as it orbits the Sun (so 366.24 rotations/y).
A quick way to see this is that the sidereal day is four minutes shorter than the civilian (solar) day, hence it takes 366 of them to fill up 365 solar days. Or look at the direction that the stars move each day, very slightly "westwards", hence causing the motion of the stars across the sky to be slightly more rapid than the motion of the sun ...