sidereal time

American  

noun

Astronomy.

1. time measured by the diurnal motion of stars. A sidereal day is about four minutes shorter than a solar day, with hours, minutes, and seconds all proportionally shorter.

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sidereal time British  

noun

1. time based upon the rotation of the earth with respect to the distant stars, the sidereal day being the unit of measurement See also sidereal day

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sidereal time Scientific  

1. Time based on the rotation of the Earth with respect to the background of fixed stars. Astronomers generally use sidereal time rather than solar time because it is better suited to observations beyond the solar system.

2. ◆ A sidereal day is the time required for one complete rotation of the Earth on its axis with respect to a fixed star. It is an unvarying unit equal to 23 hours, 56 minutes, 4.09 seconds of solar time.

3. ◆ A sidereal month is the average period of revolution of the Moon around the Earth with respect to a fixed star, equal to 27 days, 7 hours, 43 minutes of solar time.

4. ◆ A sidereal year is the time required for one complete revolution of the Earth around the Sun with respect to a fixed star, equal to 365 days, 6 hours, 9 minutes, 9.54 seconds of solar time.

5. Compare solar time

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Etymology

Origin of sidereal time

First recorded in 1805–15

Example Sentences

But one puzzling signal showed up most days at the same sidereal time.

From Scientific American • Aug. 3, 2018

Astronomers prefer sidereal time for planning their observations because in that system, a star rises at the same time every day.

From Textbooks • Oct. 13, 2016

A capital bit of horology, the pendulum of which is usually compensated to sidereal time, for astronomical purposes.

From The Sailor's Word-Book An Alphabetical Digest of Nautical Terms, including Some More Especially Military and Scientific, but Useful to Seamen; as well as Archaisms of Early Voyagers, etc. by Belcher, Edward, Sir

The driving screw having been thrown out of gear, the circle is turned until the outer vernier indicates the sidereal time, whereupon the driving screw is thrown into gear again.

From Photographs of Nebul? and Clusters Made with the Crossley Reflector by Keeler, James Edward

The equation of time and the sidereal time of mean noon complete the ephemeris proper.

From Side-Lights on Astronomy and Kindred Fields of Popular Science by Newcomb, Simon