Tracking the motion of the planets: Can a planet be followed?

From Experiment Central, published by U·X·L and available online in Science Resource Center.

Planets sometimes reflect light from the Sun, which makes them shine like stars. But unlike the stationary stars, Earth and the other planets move through the sky as they orbit the Sun. As the other planets orbit the Sun, Earth continues through its orbit. The combination of these movements can make the apparent path of the planets in Earth's sky resemble an s-shaped pattern. In this project, you will examine this phenomenon.

Level of Difficulty

Moderate. (You need to be familiar with the star positions.)

Materials Needed

• a star map for your area and time of the year
• binoculars or telescope (optional)

Approximate Budget

• $2 for a star map. (Consult local papers or magazines for current monthly maps.)

Timetable

15 to 20 minutes per night for 10 to 15 nights.

How to Experiment Safely

Always stay on level ground when star gazing. Have an adult with you

Step-by-Step Instructions

1. Examine your local star map. Most star maps should be held upside down and over your head.
2. Choose a planet that should be visible in your night sky. Locate its position on the map.
3. With or without using binoculars, try to find this planet in the night sky. Planets are usually the brightest objects in the sky and do not twinkle like stars.
4. On your star map, record the position and time you located the planet.
5. Repeat this procedure every night for 10 to 15 nights.
6. Connect the marks on the star map and trace the path of the planet.

Summary of Results

Record your results on a star map like this one. Be sure to label each star and the daily positions of the planet. After 10 to 15 nights of observations, were you able to notice the motion of the planet among the stars?

Troubleshooter's Guide

Here are some problems that may arise during this project, some possible causes, and ways to remedy the problems.

Problem: You cannot see the planets or stars.

Possible cause: The sky is too overcast. Try coming out again an hour or two later.

Problem: You cannot find the new position of the planet.

Possible cause: You might be unfamiliar with the night sky. Ask a knowledgeable adult for help, or look on the Internet for a daily star map. Locate the planet and transfer its position to your star map