As a result of the Pluto debate, astronomers realized that there was no clear definition of the word planet. There were many ideas about what a planet was and was not. Consequently, a group of astronomers from the International Astronomical Union got together and created a definition on which they could all agree. The definition states that a planet is a body that 1) moves around the sun, 2) is large enough for its own gravity to make it round, and 3) has "cleared [the] neighborhood" around its orbit of smaller objects. Under this new definition, the scientists decided that Pluto was too small to be a planet, and they changed its status to "dwarf planet."
Today, there are still varying opinions about Pluto's status. Some astronomers agree that Pluto's size makes it unworthy of the "planet" title. They are satisfied with its new designation as a dwarf planet. However, many others disagree with the new classification and think Pluto should again be counted as the ninth planet. There are respected scientists on both sides of the issue. The only thing that seems clear is that the debate will continue.
1
the astronomer who found Pluto
the discovery of Pluto
the name Pluto
2
the definition of an asteroid
the reasons why astronomers disagree
the debate about Pluto's status as a planet
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the International Astronomical Union
the definition of a planet
types of astronomical objects
4
the size of Pluto
changing the definition of a planet
different ideas about the status of Pluto