The Celestial Sphere

Imagine a large sphere encircling the Earth. On this sphere are all the stars in the sky. This is the celestial sphere, and it is a scientific model of the sky and the coordinate system of the stars visible in the night sky. By having a model of the sky in relation to the Earth, astronomers are able to see the position of stars and the paths they seem to make across the sky from day to night.

Essential Questions

• What is the celestial sphere?
• How is the celestial sphere used in the study of astronomy?