The Dwarf Planets
Some objects in the solar system look like planets, but they are smaller than planets. Astronomers call these objects dwarf planets. For many years Pluto was considered a planet. But in 2006, astronomers decided it should be called a dwarf planet. It lies in the Kuiper belt.
The Kuiper belt includes other dwarf planets, such as Eris, Haumea, and Makemake. In 2006, the United States launched New Horizons, the first space probe sent to study Pluto and other Kuiper belt objects. New Horizons should reach Pluto in 2015.
Not all dwarf planets are in the Kuiper belt. The dwarf planet named Ceres orbits the sun in the asteroid belt between Mars and Jupiter.
Picture Credit : Google