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# Mapping The Solar System

Space is big. Really big. You can see just how big it is with this activity.

Science > Earth and Space Sciences > Year 5 > ACSSU078

## You’ll need

• Several balls of twine or wool, with one at least 100 m
• A measuring wheel
• Metre rule
• A pole to tie string around (such as a broom)
• Name tags (optional)
• A large, empty space such as a school oval

## Try this

1. Select one person to be the sun. They will hold the pole that the string is tied around.
2. Using the table below, have the group measure out one piece of string for each of the planets, allowing an extra 10cm to hold the string and another 15–20cm for tying the string around the sun pole.
3. Now tie the string to the sun pole and allocate a student to each of the pieces of string to represent a planet. It might be helpful to wear name tags for the planet they represent.
4. Have the ‘planets’ line up in order of distance from the sun. Observe the distances between the planets. Is this what students expected? At this scale, the sun would be 1.3cm in diameter, or roughly the size of a marble.
5. Planets now need to compete a lap of the sun. The rest of the group can clap to keep the beat. Keeping the string lightly stretched, have the planets walk around the sun at a constant speed. Once the planets have completed a lap (equal to their planet’s year), they sit down.

 Planet Distance (m) where 1 AU = 1m Distance from the Sun (AU) Mercury 0.4m 0.4 Venus 0.7m 0.7 Earth 1.0m 1.0 Mars 1.5m 1.5 Jupiter 5.2m 5.2 Saturn 9.5m 9.5 Uranus 19.2m 19.2 Neptune 30.1m 30.1

1 Astronomical Unit (AU) = the distance from the Sun to Earth

## Further investigation

• Think about how big each of the planets would be if the sun was the size of a marble, tennis ball or basketball.
• How much further would the planets be apart if the Sun was 1m3? What size would each of the planets be?

## What’s Happening?

The distances in the Solar System are vast. We use Astronomical Units to measure distances around our solar system. One Astronomical Unit is equal to the distance between the Earth and the Sun, with one AU being equal to a mere 150 million kilometres. A planet’s year is equal to the time it takes that planet to orbit the sun. The further away a planet is, the longer it takes to orbit the sun because they have a much greater distance to travel along their orbit around the sun. Mercury has a year that lasts 88 Earth days, while Neptune’s year lasts nearly 165 Earth years. Planets travel much faster than we do, but they have much greater distances to travel.

The planets we know orbit our sun but other stars also have planets. In 2017, we had discovered over 3,600 planets orbiting 2,700 stars. It is estimated that one in five sun-sized stars have an earth-sized planet orbiting them in what we call the habitable zone. This means in roughly the same distance from the star as Earth is from the Sun. The nearest star with planets in the habitable zone is 4.2 light years (a light year is the distance travelled by light in one year) from Earth.