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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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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:

    When did Pluto become a dwarf planet?

    A:

    Pluto became a dwarf planet in 2006. Upon being stripped of its title as a planet, Pluto joined two other celestial bodies, called Eris and Ceres, in the category of dwarf planets. The decision to reclassify the former planet was made by the International Astronomical Union (IAU).

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  • Q:

    How many miles is Pluto from the sun?

    A:

    Pluto is considered a dwarf planet, and it is about 3.7 billion miles from the sun. Until it was reclassified in 2006, Pluto was the ninth and furthest planet from the sun.

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  • 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:

    Why is Pluto not considered a planet?

    A:

    Pluto is not considered a planet due to its small size and location in the solar system. Pluto is considered a dwarf planet, according to NASA.

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