Pluto is a dwarf planet of the subcategory known as plutoids, smaller than the eight "classical" planets of the Solar System and usually farther than Neptune is from the Sun. Pluto is only two-thirds as big as our own Moon and has only one-fifth of the Moon's mass. Its size had led to astronomers to question for some time whether Pluto should be called a planet at all. The debate about Pluto's status intensified in 2005 when it was shown that Eris (formerly known as 2003 UB313), an object further out in the Kuiper Belt, is larger than Pluto. On August 24, 2006, at a meeting of the International Astronomical Union (IAU) in Prague, astronomers voted to downgrade Pluto's status. It is no longer considered to belong in the same category as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Instead it has been placed in a new category of "dwarf planets." It has also been given the minor planet designation of 134340 Pluto. However, this decision to demote Pluto is opposed by several hundred astronomers. In June 2008, the IAU defined a new subcategory of dwarf planets to be known as plutoids. A plutoid is any dwarf planet that orbits beyond Neptune. Only Pluto and Eris are known to belong to this subcategory. 

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Pluto is a dwarf planet of the subcategory known as plutoids, smaller than the eight "classical" planets of the Solar System and usually farther than Neptune is from the Sun. Pluto is only two-thirds as big as our own Moon and has only one-fifth of the Moon's mass. Its size had led to astronomers to question for some time whether Pluto should be called a planet at all. The debate about Pluto's status intensified in 2005 when it was shown that Eris (formerly known as 2003 UB313), an object further out in the Kuiper Belt, is larger than Pluto. On August 24, 2006, at a meeting of the International Astronomical Union (IAU) in Prague, astronomers voted to downgrade Pluto's status. It is no longer considered to belong in the same category as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Instead it has been placed in a new category of "dwarf planets." It has also been given the minor planet designation of 134340 Pluto. However, this decision to demote Pluto is opposed by several hundred astronomers. In June 2008, the IAU defined a new subcategory of dwarf planets to be known as plutoids. A plutoid is any dwarf planet that orbits beyond Neptune. Only Pluto and Eris are known to belong to this subcategory. 

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