Elliptical Orbits

Orbits are usually elliptical, this demonstrates an easy way to draw elliptical orbits that could represent orbits of planets, asteroids and comets in the solar system.

Apparatus and Materials

• Sheet of A3 (or bigger) paper
• Cork board or similar
• Map pins
• String loops
• Various coloured pens

Health & Safety and Technical Notes

Read our standard health & safety guidance

Teaching Notes

• Drawing elliptical orbits is quite easy, and you can use this method to show the shape of planet, asteroid and comet orbits.
• You draw the ellipse by placing the string around the two map pins, and putting a pen inside the string loop and moving it around the map pins keeping the string tight at all times.
• You will find that placing the map pins quite close together will produce an almost circular orbit. Placing them further apart may at first seem to make very little difference. You have
to move the map pins quite far apart before you achieve an ellipse that is more like the orbit of a comet.
• A simple activity for a class doing this, would be for students to produce orbits that could be representative of an inner planet, outer planet and a comet.
• It can take a little bit of effort before you get orbits that are neat and tidy, but most students will pick this up in a couple of minutes.
• You can use a diagram drawn using this method to show why the Earthʼs seasons are not caused by its distance from the Sun. The Earth is closer to the Sun in the northern
hemisphereʼs winter, and further away in the northern summer. This shows that the seasons are not caused by the Earth's distance from the Sun
• It is also obvious that when it is summer in the norther hemisphere, it is winter in the southern hemisphere. Therefore, distance from the Sun is not a factor that causes the seasons.