Solar system

The Solar System is made up of the Sun and all the objects that spin around it, from planets and moons, to chunks of rock and huge amounts of dust.

The Sun

The Sun is a star; that is, a massive ball of exploding gases. It applies a pulling force, called gravity, to everything within a range of around 6,000 million km locking them into orbit around it.

The Planets

The largest things that spin around the Sun are the planets. At the moment, scientists know of nine of them, but there may be more that have not been discovered yet. They travel around the Sun in near-circular paths, called orbits. The four planets closest to the Sun, called the inner planets are small, rocky and compact. These are Mercury, Venus, Earth and Mars.

The planets farther away from the Sun are called the outer planets. These are Jupiter, Saturn, Uranus, Neptune and Pluto. They are made of ice, gas and liquids and all except Pluto are larger than the inner planets.


Asteroids are large chunks of rock, or rock and metal. They were formed along with the rest of the Solar System around 5,000 million years ago. They orbit the Sun like the planets. Some asteroids have a long, oval-shaped orbit which takes them far away from the Sun. Others travel ahead of or behind the planets, but most lie between Mars and Jupiter in a band called the Asteroid Belt.


Comets are like huge, dirty icebergs orbiting the Sun. Their paths take them far away, and then only come near the Sun for a short time. They are mostly named after who discovered them. For example, Halley's comet is named after the astronomer Edmund Halley.


Many planets have moons in orbit around them, in the same way that our Moon orbits the Earth. Some planets have many moons; for example, Saturn has at least 18.

There are different types of moons. Some are rocky; others contain ice and liquid as well as rock. Many, like our Moon, have craters, mountains and valleys.


Small pieces of debris floating around in the Solar System are called meteoroids. When they fall into the Earth's atmosphere, they burn up and make a bright streak across the sky. Falling meteoroids are called meteors. Some meteors actually hit the Earth's surface. These are called meteorites.