The celestial equator is currently inclined by about 23.44° to theecliptic plane. The image shows the relations between Earth'saxial tilt (orobliquity),rotation axis, andorbital plane.
An observer standing on Earth'sequator visualizes the celestial equator as asemicircle passing through thezenith, the point directly overhead. As the observer moves north (or south), the celestial equator tilts towards the oppositehorizon. The celestial equator is defined to be infinitely distant (since it is on the celestial sphere); thus, the ends of the semicircle always intersect the horizon due east and due west, regardless of the observer's position on Earth. At thepoles, the celestial equator coincides with the astronomical horizon. At alllatitudes, the celestial equator is a uniform arc or circle because the observer is only finitely far from the plane of the celestial equator, but infinitely far from the celestial equator itself.[3]
Astronomical objects near the celestial equator appear above the horizon from most places on earth, but theyculminate (reach the meridian) highest near the equator. The celestial equator currently passes through theseconstellations:[4]
These are the most globally visible constellations.
Over thousands of years, the orientation of Earth's equator and thus the constellations the celestial equator passes through will change due toaxial precession.
Celestial bodies other than Earth also have similarly defined celestial equators.[5][6]
