Sun and its planets. Artwork of the eight planets of the solar system arrayed from left to right in their order from the Sun (far left). The size of the Sun and planets is to scale. The four small, rocky planets of the inner solar system are Mercury, Venus, Earth and Mars. The four large, gas giant planets of the outer solar system are Jupiter, Saturn, Uranus and Neptune. In August 2006, Pluto (not shown) became a Dwarf planet. Planetary rings and moons, a solar flare (behind Jupiter) and the Milky Way (bright band behind the planets) are also shown. The Sun, a star in the Milky Way, contains 99.9% of the mass of the solar system.