On August 24th, 2006, Pluto was officially demoted from being a planet, which apparently caused some people to be outraged.

Pluto didn’t meet the final rule, as Britannica writes:

So, what was the IAU’s reason for demoting Pluto when it did? Why is Pluto no longer a planet?

The main event of the 2006 General Assembly of the IAU, the proposal that would come to demote Pluto, was a defining moment for the rest of the solar system as well. Fiercely debated by the members of the union, the resolution that was passed officially defined the term planet . What was once a loose word used to describe a large object within the solar system was now specific: planets are celestial objects large enough to be made rounded by their gravitational orbit around the Sun and to have shooed away neig

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