celestial meridian

American  

[suh-les-chuhl-muh-rid-ee-uhn] / səˈlɛs tʃəl məˈrɪd i ən /

noun

1. Astronomy. the line on the celestial sphere that passes through the observer's zenith and connects the north and south celestial poles.

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celestial meridian Scientific  

1. A great circle on the celestial sphere passing through the celestial poles and an observer's zenith. An observer's celestial meridian is not a fixed reference on the celestial sphere but rather changes with the observer's location on Earth. Stars transit an observer's celestial meridian (that is, cross directly overhead in the sky at that location) once every 24 hours.

2. Also called local meridian meridian

3. In the equatorial coordinate system, a great circle on the celestial sphere passing through the celestial poles and the vernal equinox. It represents the zero point for the horizontal coordinate in this system, having a right ascension of 0 hours.

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Example Sentences

We may remember in passing that the length of the meter has been determined as, by definition, the ten-millionth part of the quarter of a celestial meridian.

From Astronomy for Amateurs by Welby, Frances A. (Frances Alice)

With our sextants we find when the centre of the sun is on the celestial meridian corresponding to the terrestrial one; and at that instant it is noon where we are.

From Across India Or, Live Boys in the Far East by Optic, Oliver