<Dl> <Dd> Ceres (2.77 AU) is the largest asteroid, a protoplanet, and a dwarf planet . It has a diameter of slightly under 1,000 km, and a mass large enough for its own gravity to pull it into a spherical shape . Ceres was considered a planet when it was discovered in 1801, and was reclassified to asteroid in the 1850s as further observations revealed additional asteroids . It was classified as a dwarf planet in 2006 when the definition of a planet was created . </Dd> </Dl> <Dd> Ceres (2.77 AU) is the largest asteroid, a protoplanet, and a dwarf planet . It has a diameter of slightly under 1,000 km, and a mass large enough for its own gravity to pull it into a spherical shape . Ceres was considered a planet when it was discovered in 1801, and was reclassified to asteroid in the 1850s as further observations revealed additional asteroids . It was classified as a dwarf planet in 2006 when the definition of a planet was created . </Dd> <Dl> <Dd> Asteroids in the asteroid belt are divided into asteroid groups and families based on their orbital characteristics . Asteroid moons are asteroids that orbit larger asteroids . They are not as clearly distinguished as planetary moons, sometimes being almost as large as their partners . The asteroid belt also contains main - belt comets, which may have been the source of Earth's water . </Dd> </Dl> <Dd> Asteroids in the asteroid belt are divided into asteroid groups and families based on their orbital characteristics . Asteroid moons are asteroids that orbit larger asteroids . They are not as clearly distinguished as planetary moons, sometimes being almost as large as their partners . The asteroid belt also contains main - belt comets, which may have been the source of Earth's water . </Dd>

List of planets and their distance from the sun