Jupiter is the largest planet in the Solar System. Jupiter orbits the Sun at a distance of 778 million km (483 million miles)!! Jupiter is so large that 1,000 planets the size of the Earth could fit into it! That's a whole lot of Earths! Jupiter is one of the four planets that are made mostly of gas. The others are Saturn,Uranus,and Neptune. Did you know that Jupiter has 16 moons?