sidereal time

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.

sidereal time

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

sidereal time

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

Word History and Origins

Origin of sidereal time¹

First recorded in 1805–15

Example Sentences

If the clock gains or loses with respect to sidereal time, take this into account in the value of U.

From Project Gutenberg

When the hour circle passing through Sirius coincides with the meridian, the sidereal time is 6h.

From Project Gutenberg

The sidereal time at any moment is the right ascension of the hour circle which at that moment coincides with the meridian.

From Project Gutenberg

Having set the clock approximately to sidereal time, observe one or two more stars in the same way as above.

From Project Gutenberg

Sidereal time was determined by observing transits of stars over a meridian line actually laid out upon the ground, etc.

From Project Gutenberg