The celestial equator is an imaginary line that divides the sky into the northern and southern celestial hemispheres. It is directly above the Earth's equator and extends out into space, serving as a reference point for astronomers. This line helps in locating stars and other celestial objects in the sky. As the Earth rotates, the celestial equator appears to move across the sky, making it an essential tool for navigation and understanding the positions of celestial bodies. It is also used in conjunction with the ecliptic, which is the path the Sun takes through the sky over the course of a year.