There are eight planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Formerly, Pluto was considered the ninth planet, but it was reclassified as a "dwarf planet" by the International Astronomical Union in 2006. The planets vary widely in size, composition, and characteristics. For example, Mercury is the smallest and closest to the Sun, while Jupiter is the largest planet known for its Great Red Spot. The planets are divided into two categories: terrestrial (rocky) planets, which include Mercury, Venus, Earth, and Mars, and gas giants, which include Jupiter, Saturn, Uranus, and Neptune.