Jupiter is the largest of all the planets, followed by Saturn, Uranus, Neptune, the Earth, Venus, Mars, Pluto and Mercury, the smallest. Many of the planets have their own small moons revolving around them, just like the Earth's moon. Two of Jupiter's moons, called Ganymede and Callisto are larger than Mercury. Jupiter has at least eleven other moons or satellites and more may yet be discovered. Saturn has ten satellites but is more famous for the beautiful rings that surround it. These rings are only a few kilometres thick and are made up of small chunks of ice and rocky material. Scientists used to think that only Jupiter had rings, but it was recently discovered that Uranus too, had a system of rings. Our knowledge of the planets has greatly increased, and as space probes become more sophisticated, we will probably find out more about the planets in years to come.

Jupiter's atmosphere resembles that of the Sun, made up mostly of hydrogen and helium. A helium-rich layer of fluid metallic hydrogen envelops a “fuzzy” or partially-dissolved core at the centre of the planet.

The colourful light and dark bands that surround Jupiter are created by strong east-west winds in the planet's upper atmosphere travelling more than 335 mph (539 km/h). The white clouds in the light zones are made of crystals of frozen ammonia, while darker clouds made of other chemicals are found in the dark belts. At the deepest visible levels are blue clouds. Far from being static, the stripes of clouds change over time.