On 24 August 2006, the International Astronomical Union created a clear definition of what constitutes a planet. (Before this, there was no clear definition of what an object needed to count as a planet or not.)
The definition stated that a planet:
- is in orbit around the Sun,
- has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
- has "cleared the neighborhood" around its orbit.
By this definition, Pluto (which had long been considered a planet) was no longer counted as a planet. Instead, it was placed into a category called "Dwarf Planet", since it fit only the first two criteria.
My challenge is this:
Does reclassifying Pluto to be a dwarf planet change our scientific understanding of Pluto in any way? If so, what way?