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Why is Pluto not a planet?

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Quick Answer

In 2006, the International Astronomical Union changed Pluto's classification from a planet to a dwarf planet because the planet has not cleared its orbit of other objects. When a planet clears its orbit, all other objects on the orbital path are either drawn into the planet's gravitational pull or flung away from it and out of the orbit.

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Why is Pluto not a planet?
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Full Answer

The change in classification came after the discovery of the dwarf planet Eris in 2005. Eris is more massive and Pluto and orbits the sun, so its discovery challenged the notion of a nine-planet solar system. To account for the discovery of Eris and the subsequent discovery of other bodies, the International Astronomical Union created the dwarf planet classification. By definition, Pluto best matches the characteristics of a dwarf planet and was reclassified as one. Pluto could potentially clear its orbit in the future, most likely by colliding with other objects in its orbit and combining with them, which would give it back its planet classification. As of 2014, the other named dwarf planets besides Pluto and Eris are Ceres, Makemake and Haumea. According to NASA, there may be over 100 as-yet undiscovered dwarf planets in the solar system, which covers objects with sufficient mass to achieve a round shape and that orbit the sun.

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Related Questions

  • Q:

    Is Pluto still called a planet?

    A:

    Pluto is referred to as a "dwarf planet" because of its location in space and its tiny size, which makes it unable to move other objects out of its orbit. Astronomers began calling Pluto a dwarf planet in 2003 when an astronomer observed a new, larger object beyond Pluto, which he named Eris.

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  • Q:

    Does Pluto have craters?

    A:

    Pluto, a dwarf planet, is subject to impact from cosmic material, which is the cause of planetary "craters." Pluto, however, is not close enough to Earth for modern imaging techniques to specifically identify these craters. They are assumed to exist.

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  • Q:

    How many satellites does Pluto have?

    A:

    The dwarf planet Pluto has five satellites or moons. Their names are Nix, Styx, Hydra, Kerberos and Charon. Pluto's largest moon is Charon, which was discovered in 1978. Pluto is about a half size larger than Charon.

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  • Q:

    What are some interesting facts about Pluto?

    A:

    Pluto is a dwarf planet in the area of the Kuiper belt, which is an area with many dwarf planets, according to the National Aeronautics and Space Administration (NASA). The dwarf planet is after Neptune in the planetary alignment, and it is the former ninth planet until reclassification in 2006, clarifies the Space Telescope Science Institute.

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