Table of Contents

Circumpolar Motion

Module 1: Introduction to the Day and Night Sky

Button controls:

• (1) Help button:
  • This button will open a window with help information
• (2) Show/Hide constellations:
  • This button will add constellation lines to the stars depicted
• (3) Controller buttons:

• (A) Reset: reload the applet and reset the parameters
• (B) Rewind: press and hold to advance the applet in reverse
• (C) Pause: temporarily stop the action in the applet
• (D) Play: begin or resume the action in the applet
• (E) Fast Forward: press and hold to advance the applet
• (F) End: advance the applet to its end
• (G) Speed: click to select the number and input a higher number to increase the speed of the rewind and fast forward buttons
• (H) Slider bar: shows the progression through the animation
• (I) Drag controller: click and drag over this symbol to reposition the controller buttons within the applet frame
• (J) Collapse button: click this button to collapse controller button

Using the applet:

This applet has been designed to help students visualize the concept of the circumpolar motion of the stars. It consists of four key components: the star field; the pole star (4); the hour indicators (5); and the constellations.

Circumpolar motion is the apparent rotation of all the stars in the northern hemisphere around the pole star, Polaris. The positions of the stars remain constant with respect to each other; therefore, the constellations maintain their shapes. The stars make one complete rotation every 24 hours (one day).

The horizon line is used to reinforce the notion that not all stars are circumpolar. The height of the hoizon line depends upon the observer's latitude on the Earth.