Sidereal time
Sidereal timeis a time-keeping system. It is used byastronomersto findcelestialobjects. Using sidereal time it is possible to point a telescope to the proper coordinates in the night sky.
Sidereal time is a "time scale based on Earth's rate of rotation measured relative to the fixed stars".[1]
Because the Earth moves in its orbit about the Sun, a meansolar dayis about four minutes longer than asidereal day.Thus, a star appears to rise four minutes earlier each night, compared to solar time. Different stars are visible at different times of the year.
Bycontrast,solar timeis reckoned by the movement of the Earth from the perspective of theSun.An average solar day (24 hours) is longer than a sidereal day (23 hours, 56 minutes, 4 seconds) because of the amount the Earth moves each day in itsorbitaround the Sun.
Related pages
[change|change source]References
[change|change source]
