Both solar time and sidereal time make use of the regularity of Earth's rotation about its polar axis: solar time is reckoned according to the position of the Sun in the sky while sidereal time is based …

The meaning of SIDEREAL is of, relating to, or expressed in relation to stars or constellations : astral.

SIDEREAL definition: determined by or from the stars. See examples of sidereal used in a sentence.

Jun 10, 2012 · Sidereal time measures the rotation of our planet relative to the stars. It allows astronomers to keep time without worrying about the motion of Earth around the sun.

1. Of, relating to, or concerned with the stars or constellations; stellar. 2. Measured or determined by means of the apparent daily motion of the stars: sidereal time.

Sidereal time, time as measured by the apparent motion about the Earth of the distant, so-called fixed, stars, as distinguished from solar time, which corresponds to the apparent motion of the Sun.

By convention, rotation periods of planets are given in sidereal terms unless otherwise specified.

sidereal, adj. meanings, etymology, pronunciation and more in the Oxford English Dictionary

Feb 2, 2026 · (astronomy) Relating to a measurement of time relative to the point of the vernal equinox.

2 meanings: 1. of, relating to, or involving the stars 2. determined with reference to one or more stars....