Sun and the planets. Illustration comparing the size of the Sun and its planets. Most of the mass of the Solar System is found in the Sun (partially seen in background). The planets are arranged in two groups, the inner planets (top right) and the outer planets (centre and left). The sizes are to scale and they are ordered (from right to left) by distance from the Sun. From left to right, the outer planets are: Neptune, Uranus, Saturn and Jupiter. From left to right, the inner planets are: Mars, Earth, Venus and Mercury. The Sun's diameter (1.4 million kilometres) is around 109 times that of Earth and around 10 times that of Jupiter.