The Solar System is made up of the Sun, nine planets, several moons (the number changes as more are discovered) and a band of rocks called the Asteroid Belt. The planets and the Asteroid Belt all travel round the Sun. we say they ‘orbit’ the Sun. They each take a certain time to round the Sun. The time is the planet’s ‘year’. As the planets orbit, they themselves spin. They all spin at different speeds. The time they take to spin round once is called a ‘day’. Many of the planets have moons. While the planets orbit the Sun, the moons orbit the planets.
All the planets are different sizes. The Sun is so big compared to the planets that only a tiny part of it fits on the page!
The planets vary greatly in size and all are a very long way from the Sun. The planets closest to the Sun have the shortest years as they do not have as far to travel. The planets with the shortest days are the ones that spin round fastest.