celestial equator

noun

, Astronomy, Navigation.

1. the great circle of the celestial sphere, lying in the same plane as the earth's equator.

celestial equator

noun

1. the great circle lying on the celestial sphere the plane of which is perpendicular to the line joining the north and south celestial poles Also calledequinoctialequinoctial circle

celestial equator

1. A great circle separating the northern and southern hemispheres of the celestial sphere and lying in the same plane as the Earth's equator. The celestial equator is a projection of the Earth's equator outward onto the celestial sphere and is used as the reference point in determining a celestial body's declination .

Word History and Origins

Origin of celestial equator¹

First recorded in 1870–75

Example Sentences

Fall officially kicks off Friday at 11:50 p.m. with the fall equinox, the moment the sun crosses the celestial equator, an imaginary line above earth’s equator.

From Seattle Times

Standing by the Hunter’s foot, the Great Dog is an easy-to-find constellation visible from most areas of the world, thanks to being positioned just south of the celestial equator.

From National Geographic

And whereas Ptolemy based his coordinate system on the ecliptic, Hipparchus used the celestial equator, a system more common in modern star maps.

From Scientific American

This makes the sun appear at its farthest below the celestial equator when viewed from Earth.

From Seattle Times

At the instant of the equinox — and it’s only an instant — the sun will beam directly above the celestial equator, that imaginary line that divides the planet in two.

From Seattle Times