How many planets are in the Solar System?

The four inner planets — Mercury, Venus, Earth and Mars — are small and rocky. The four outer planets are giants: Jupiter and Saturn are gas giants, while Uranus and Neptune are ice giants. In 2006 the International Astronomical Union defined a planet as a body that orbits the Sun, is round due to its own gravity and has cleared its orbital neighbourhood. Pluto fails the third test because it shares its region with many Kuiper Belt objects, so it became a dwarf planet. Other recognised dwarf planets include Ceres, Eris, Haumea and Makemake.