Which specific criterion, required by the new 2006 definition, did Pluto ultimately fail to satisfy?

Answer

Have cleared the neighborhood around its orbit

The modern, scientifically binding definition established in 2006 requires a celestial body to meet three distinct conditions to be classified as a planet within our solar system. While bodies like Pluto successfully meet the first two criteria—orbiting the Sun and achieving hydrostatic equilibrium (a nearly round shape due to self-gravity)—it failed the third requirement. This crucial third step mandates that the body must have 'cleared the neighborhood' around its orbit. This means the object must be gravitationally dominant along its orbital path, having either swept up or ejected other smaller bodies sharing that zone. Pluto's failure here, due to its location among numerous other large Kuiper Belt Objects that share its orbital vicinity, is what relegated it to the dwarf planet category, highlighting the shift from a descriptive standard to a dynamic one.

Which specific criterion, required by the new 2006 definition, did Pluto ultimately fail to satisfy?

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