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Last Post 18 Oct 2012 09:23 AM by  Paulett Liewer
Why is pluto not a planet
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17 Oct 2012 02:53 PM
    Why is pluto not a planet if it is bigger than mercury
    Tags: Pluto, dwarf planet

    Paulett Liewer



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    Posts:113
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    17 Oct 2012 03:41 PM

    Good question... but there's more to being a planet than just size. Three requirement were set by the International Astronomical Union (IAU) in 2006.for an object to be called a planet:

    The body

    1) Is in orbit around the Sun (or star)
    2) Has sufficient mass to assume hydrostatic equilibrium (a nearly round shape)
    3) Must be gravitationally dominant enough (massive enough) to prevent anything of similar size, barring its own satellites, from floating around the planet. The term that the IAU used was “clearing the neighborhood of its orbit,” which was one of the most important aspects of the definition that was debated

    Mercury meet all three requirements, so it's classified as a planet.
    Pluto meets the first two, but apparently NOT the last one.

    Object that meet the first two (but not the last) are now called Dwarf Planets. The object UB313 ( Xena) is a dwarf planet LARGER than Pluto.


    Paulett Liewer



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    Posts:113
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    18 Oct 2012 09:23 AM

    I should have caught this sooner: Mercury is much bigger than Pluto. More than twice by diameter and much more by size and mass.

    Paulett

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