At 120,000 kilometers in diameter, Saturn is the solar system's largest planet. Like Jupiter it is a gas giant made up chiefly of hydrogen around a small rocky core. It has at least 30 moons, more than any other planet. Cloud formations are less complex and striking than on Jupiter, although wind speeds are much greater. First observed by Galileo in 1610, Saturn's ring system is the largest, most complex and best studied of all the gas giants. The Voyager 1 spacecraft took this photograph in 1980 and it has been colour enhanced.