Dwarf planets are smaller than planets, but larger than comets or meteors. They orbit only the sun, and they are not moons or satellites. Their mass is large enough for their gravitational pull to cause them to become almost spherical. However, they are not massive enough for their gravitational pull to sweep their region's of orbit almost free of other objects. Dwarf planets are in a separate group from planets. They were discovered by the International Astronomical Union. Some of the most known dwarf planets are Pluto, Ceres, and Eris, but Astronomers expect more to be discovered. Dwarf planets are found in the Kuiper belt and were called "Kuiper belt objects" for a long time.
The Kuiper belt is home to more than 100 billion objects. It begins at 2.8 billion miles from the sun, and it's outer edge is 4.6 billion miles from the sun.
Eris is the largest dwarf planet. It is about 1,500 miles in diameter. The smallest dwarf planet has not yet been identified.
Pluto used to be known as a planet, but was made a dwarf planet in 2006. It was originally discovered in 1936 by Clyde W. Tombaugh. Pluto also orbits the Kuiper belt.
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