celestial sphere

American  

noun

1. the imaginary spherical shell formed by the sky, usually represented as an infinite sphere, the center of which is a given observer's position.

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celestial sphere British  

noun

1. an imaginary sphere of infinitely large radius enclosing the universe so that all celestial bodies appear to be projected onto its surface

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celestial sphere Scientific  

1. An imaginary sphere with Earth at its center. The stars, planets, Sun, Moon, and other celestial bodies appear to be located on this sphere, and the sphere appears to rotate around the Earth's extended axis once every 24 hours, carrying the celestial bodies with it overhead and giving them their diurnal motions. The celestial sphere is essentially a spherical map of the sky that provides the basis for the coordinate systems used in celestial navigation and in specifying the positions and motions of celestial objects.

2. See more at altazimuth coordinate system ecliptic coordinate system equatorial coordinate system

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Etymology

Origin of celestial sphere

First recorded in 1875–80

Example Sentences

Believing that spacetime is a real, physical entity is no more defensible than believing in the old idea of a celestial sphere.

From Science Daily • Nov. 2, 2025

But from a terrestrial perspective, the celestial sphere appears essentially unchanging.

From Scientific American • Aug. 29, 2023

But there’s no need to be perfectly versed in every detail of the celestial sphere.

From New York Times • Jan. 1, 2023

But like the Sun, they have independent motions among the stars, superimposed on the daily rotation of the celestial sphere.

From Textbooks • Oct. 13, 2016

“The Lord of Destruction is surrounded by a celestial sphere that can only be shattered by an immortal device like those weapons.”

From "Aru Shah and the End of Time" by Roshani Chokshi