The closest planet from the Sun is Mercury and the furthest is Pluto ( called the Dwarf Planet ). The 4 planets closest to the Sun ( Mercury, Venus, Earth, Mars ) are the inner planets, made up mainly of rock and much denser than the 4 outer planets. The outer planets are called the Gas giants ( Jupiter, Saturn, Uranus and Neptune ). They are made up mostly of gasses with smaller solid and liquid centers. The planets are created in a cloud of gas and dust ( a Solar nebula ). The center of the cloud became a star - the Sun. Closer to the center could stand only rocky material ( the inner planets ) and in the outer regions was icy material that creates the Gas giants.Because of it`s position in the Solar nebula, the proto-Jupiter became the biggest of the planets. From the Jupiter the planets became massive. Those formed closer to the proto-Sun were smaller and rocky.
