In what year did the IAU formalize the definition incorporating the 'clearing the neighborhood' criterion?

Answer

2006.

The International Astronomical Union (IAU) formalized the definition that includes the requirement for clearing the neighborhood specifically in 2006, largely as a means to address the classification of objects like Pluto.

In what year did the IAU formalize the definition incorporating the 'clearing the neighborhood' criterion?

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Clearing the neighbourhood - YouTube

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