 In addition to the eight main planets in our solar system, there are a number of large bodies too small to clear the debris in their orbit. These are called minor or dwarf planets. We know of five, but there could be dozens more. Here are three of them. Pluto, with its methane ice surface, is out in the Kuiper Belt at 7.5 billion kilometers. That's 4.7 billion miles from the Sun. At that distance, it takes almost 250 years for one revolution. Pluto is 450 times smaller than the Earth. It was reclassified as a dwarf planet in 2006, when other objects its size were discovered. Chiron is the largest of Pluto's five moons. With an unexpectedly interesting surface, it is half the size of Pluto. This photograph was taken by the New Horizons spacecraft in 2015. Ceres, the only dwarf planet in the asteroid belt, is 414 million kilometers. That's 257 million miles from the Sun. It was discovered in 1801 and classified as an asteroid. Once the dawn spacecraft entered orbit around Ceres in 2015, and its true size was understood, it was reclassified as a dwarf planet. Its diameter is approximately 945 kilometers, or 587 miles, making it around 14 times smaller than Pluto. Maki Maki was discovered in 2005 by a team at the Palomar Observatory. It is in the Kuiper Belt at 7.8 billion kilometers, or 4.8 billion miles. It is thought that Maki Maki's reddish-brown color comes from a layer of methane at its surface.