Our solar system was formed about 4.5 billion years ago! But what exactly is the solar system? It consists of our sun and eight main planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. There are also moons, dwarf planets, asteroids, comets, rocks and dust.
Planets
All of the planets in the solar system orbit the sun. Mercury, Venus, Earth and Mars are called 'terrestrial planets'. They are mostly made of rock and metal. Jupiter, Saturn, Uranus and Neptune are called 'gas giants'. They are mostly composed of gas and they have rings. The smallest planet is Mercury and the biggest is Jupiter. Neptune is the coldest and Venus is the hottest planet.