Celestial equator

Definition

The celestial equator is an imaginary projection of Earth's equator into space. It divides the sky into the northern and southern celestial hemispheres.

5 Must Know Facts For Your Next Test

1. The celestial equator is always directly above Earth's equator.
2. It intersects the ecliptic at two points known as the equinoxes.
3. Stars and celestial objects near the celestial equator are visible from both hemispheres.
4. Right Ascension in the celestial coordinate system is measured along the celestial equator.
5. The celestial equator moves slightly due to axial precession over long periods.

Review Questions

• What is the relationship between Earth's equator and the celestial equator?
• How does the celestial equator relate to the concept of right ascension?
• Why are stars near the celestial equator visible from both hemispheres?

Related terms

ecliptic: The apparent path of the Sun across the sky over a year, intersecting with the celestial equator at two points.

right ascension: A coordinate used to measure positions of celestial objects along the celestial equator, analogous to longitude on Earth.

equinox: Points where the ecliptic intersects with the celestial equator, occurring twice a year when day and night are approximately equal.