The Celestial Equator

The celestial equator is a make-believe line in the sky. It lines up with Earth's equator down on the ground. If you could stretch Earth's equator out into space, it would become the celestial equator. Scientists use it to find stars and planets.

A Line in the Sky

Just like maps of Earth have lines on them, sky maps do too. The celestial equator splits the sky into a top half and a bottom half. The top half is the northern sky. The bottom half is the southern sky. Stars on this line rise straight up in the east and set straight down in the west.

Why It Is Useful

Astronomers use the celestial equator to find things in the sky. They measure how far a star is above or below the line. This helps them point their telescopes. The Sun crosses the celestial equator two times each year. These days are called the equinoxes, and they happen in March and September.

Fun Facts

• The celestial equator is not a real line you can see.
• The Sun is on the celestial equator on the first day of spring.
• People at Earth's equator can see the celestial equator pass right over their heads.

Did You Know?

The North Star sits far above the celestial equator. It marks the spot almost directly above Earth's North Pole.