Question

Due to what reasons was Pluto declared a dwarf planet and when?

Answer 1

In August 2006 the International Astronomical Union (IAU) downgraded the status of Pluto to that of "dwarf planet." This means that from now on only the rocky worlds of the inner Solar System and the gas giants of the outer system will be designated as planets.

Answer 2

Pluto was declared as a draw planet because it does not have a proper size and not a proper orbit.