Astronomy Activity Solar System Distances

SNC1D RHSA – Astronomy Page: _____

Activity – Distances in the Solar System

How large is our solar system? To help us get an idea for distances in space, we will attempt to create a scale model of the distances between the planets in our solar system with us representing the planets.

Part I. Introductory Thinking and Questions: Materials: 1 piece of paper, pen or pencil, ruler

The planets of our solar system, in order of their distance away from the sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

In groups of 3, on a piece of paper (lined or blank), draw dots representing the relative distances of the planets with respect to the sun, based entirely on your perceptions. Use the left hand edge of the paper as the position of the sun.

Use a scale of 1 mm = 1 million km. (i.e. 5 mm represents 5 million km, 20 mm represents 20 million km, etc.)

Discuss with your group members and modify your drawings until everyone in your group is satisfied. With the use of a ruler, measure and write down the spacings in the table below:

Distance to the Sun (in mm) Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

Part II. Space Distances and Scale Models The actual average distance of each planet to the sun is shown in Table 1 below. Notice that distances are in millions (106) of kilometers.

Table 1: Distance to the Sun (in millions of km) Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

57.9 108 150 228 778 1427 2870 4497

In science, as in many other areas of life, we make use of models to represent things which are either too small or too large visualize. Scale models are models which attempt to accurately represent details, such as distances between planets, in the proper relationship. Using the same scale of 1 mm = 1 million km, try to draw the proper positions of the planets on the same piece of paper as your group’s initial guesses. Question: What problem did you find when you tried to do this task? SNC1D RHSA – Astronomy Page: _____

Part III. Astronomical Units An astronomical unit (a.u.) is defined as the distance from the earth to the sun (150 million km). So the distance from the earth to the sun is 1 a.u. This is a convenient way of representing large distances in our solar system.

Example Calculation: To find the number of astronomical units between the sun and Saturn, take the distance in millions of km and divide by 150.

Distance between sun and Saturn: 1427 million km Distance between the sun and Saturn, in astronomical units: a.u.

In other words, Saturn is about 9.5 times farther away from the sun than the earth is.

Using the distances in millions of km from Table 1, complete Table 2.

Table 2: Distance to the Sun (in astronomical units) Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

1. How much farther away from the Sun is Jupiter, compared to Earth?

2. How much farther away from the Sun is Neptune, compared to Saturn?

3. Why do you think it might be more convenient to use astronomical units rather than km to compare distances in the solar system?