Table of Contents

The Celestial Sphere

Module 1: Introduction to the Day and Night Sky

Buttons and controls:

• (1) Help button:
  • This button will open a window with help information
• (2) Toggle controls:
  • Hide/Show planet - This button will display the planets along the Ecliptic
  • Stop/Start Earth - This button will stop the rotation of the Earth

Using the applet:

This applet has been designed to help students visualize the concept of the celestial sphere.

It consists of 3 key components:
the Earth (3); the Ecliptic (4); and the Celestial Sphere (5).

The Celestial Sphere can be imagined as a giant sphere enclosing the Earth. As the Earth rotates on its axis, the Celestial Sphere remains stationary. Therefore, on the Earth it appears as though the stars are "fixed" on the Celestial Sphere.

Stars appear to rotate around the celestial poles. Stars closest to the celestial equator rotate fastest, and stars nearer to the poles rotate slowest.

The planets, Moon, and Sun are all located along the ecliptic; however, their positions are not fixed on the celestial sphere.