Let's see the smartness :PP
Most Helpful Guy
Pluto is considered a dwarf planet instead of a planet for the following reasons:
1) It has next to no atmosphere making it more like an asteroid or a moon in that regard
2) The plane of its orbit differs from the rest of the planets which share a common plane.
3) Most importantly, there are a substantial number of objects in solar orbit beyond Pluto's orbit that are of similar scale to Pluto. If Pluto is a planet, then these are planets too. How many objects lie in this belt is open to debate and interpretation. Some may be large asteroids. Nothing is as large as a planet, unless you include Pluto, in which case, there may be as many as 200 or more additional "planets" in solar orbit. Basically, if Pluto was all alone, then calling it a planet was reasonable. But since Pluto seems to be bringing so many "friends" to the planetary mixer, it's best to just revoke it's ticket and call it a dwarf planet.1