Why Pluto went from Planet to Dwarf Planet

Why has Pluto has gone from being a planet to a dwarf planet? This video explains why as well as the definition of planets and dwarf planets, a includes details about the dwarf planets in our solar system. The change came about when in 2005 Eris, an object with similar dimensions but around 25% more mass than Pluto, was discovered in a similar orbit to Pluto, in whats now called the Kuiper Belt. In 2006, the International Astronomical Union created firm definitions for planets and dwarf planets. A similar thing happened in the 1800s when between the orbits of Mars and Jupiter was discovered Ceres, Juno, Vesta and Pallas. They were then called planets until many more objects were discovered in the same orbit and they were all demoted to asteroids and the Asteroid Belt. Now Pluto, Eris, Ceres, Makemake and Huamea are all classified as dwarf planets.\r
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To check if Pluto is still a Dwarf Planet go to:\r
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See also:\r
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New Years in the Solar System or How long Planets take to Orbit the Sun (1280x720)\r
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How a Rocket Works/Earth to Space Eg SpaceX Falcon 9 and Dragon (1280x720)\r
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Solar Energy - Nuclear Fusion in the Sun\r
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Some sun and planet images courtesy of NASA.\r
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Some sound effects: licensed under the Creative Commons 0 License.