1The Sun and the planets
The Solar System is the Sun and everything that orbits it. There are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, in order from the Sun.
Solar Systemplanet
Lesson 30.2 notes
The Solar System
The Sun, its eight planets and their orbits, moons, asteroids, comets and satellites, and the scale of it all.
2Rocky and giant
The four inner planets are small and rocky. The four outer planets are giants, made mostly of gas and ice. About 1300 Earths would fit inside Jupiter.
3Orbits and years
A planet's year is the time it takes to orbit the Sun once. The further out a planet is, the longer its path and the slower it moves, so the longer its year.
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4Mostly empty space
If the Sun were a football, the Earth would be a peppercorn 24 m away, and Neptune would be about 700 m away. The Solar System is mostly empty space.
5Moons
A moon is a natural object that orbits a planet. The Earth has one. Mercury and Venus have none, Jupiter has more than 90, and Saturn more than 200.
moon
6Asteroids and comets
Asteroids are lumps of rock and metal, most in a belt between Mars and Jupiter. Comets are balls of ice and dust; near the Sun, the ice turns to gas and they grow tails.
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7Artificial satellites
People have launched thousands of artificial satellites into orbit round the Earth. They're used for weather forecasts, phones and TV, satellite navigation, and looking out into space.
artificial satellite
Explore: Orbit lab
Watch the planets go round at their true speeds, speed up time, and pick any planet to see its year. Then drag your own planet closer to the Sun or further away.
Common mistake: The planets aren't close together
Pictures squash them up to fit on a page. In real life the planets are tiny next to the huge gaps between them: sunlight takes 8 minutes to reach the Earth, and over 4 hours to reach Neptune.
Remember
- The eight planets, in order from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
- The four inner planets are small and rocky; the four outer planets are giants, made mostly of gas and ice.
- The further a planet is from the Sun, the longer its year: 88 days for Mercury, 165 years for Neptune.
Going further at GCSE