The *definition of planet* set in Prague <https://en.wikipedia.org/wiki/Prague> in 2006 by the International Astronomical Union <https://en.wikipedia.org/wiki/International_Astronomical_Union> (IAU) states that, in the Solar System <https://en.wikipedia.org/wiki/Solar_System>, a planet <https://en.wikipedia.org/wiki/Planet> is a celestial body <https://en.wikipedia.org/wiki/Celestial_body> which: 1. is in orbit <https://en.wikipedia.org/wiki/Orbit> around the Sun <https://en.wikipedia.org/wiki/Sun>, 2. has sufficient mass to assume hydrostatic equilibrium <https://en.wikipedia.org/wiki/Hydrostatic_equilibrium> (a nearly round shape), and 3. has "cleared the neighbourhood <https://en.wikipedia.org/wiki/Clearing_the_neighbourhood>" around its orbit. Pluto lacks the mass to clear the neighborhood in the vicinity of it's orbit. On Mon, Jul 20, 2015 at 12:58 PM, <baxman2@q.com> wrote:
I would personally favor Pluto being returned to official Planet status for the following reasons. It is spherical, has five months, and surface geological activity. The only argument against it, is Pluto's size being smaller than Earth's Moon, making it somewhat comparable to a number of known minor planets.