Learning Objective: In this activity students explore the properties of ellipses and orbital parameters.

Specific Science Content Standards

• Position/motion of objects Earth in the solar system Changes in Earth and sky (K-4)
• Origins and evolution of the solar system

Space Update: Solar System

Introducing the activity:
Ask students what is an ellipse. Most will know what an oval is. They may know what an "eccentric" ellipse is, but most will not guess that an ellipse of eccentricity of 0.25 still appear quite circular to the eye - just the foci are offset from the center.

Extending the activity:
Have students calculate eccentricity and semimajor axis from aphelion and perihelion, or vice versa. Calculate these for the moons of the planets.