In the end around 2700 astronomers agreed that the solar system be divided into two categories called 'Planet' and 'Dwarf Planet'. Pluto being put in the category of 'Dwarf Planet' that means it will no longer be placed in the company of eight planets viz. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called 'Dwarf planets was decided with Ceres, Pluto and 2003 UB313 (temporary name) being the first three members of this club.
When Pluto was discovered, in 1930 astronomers assumed that it had a mass comparable to Earth's. Only gradually, in the ensuing decades, did celestial mechanicals come to realize that this grossly overestimated. Pluto turned out to be less than 1% of Earth's size.
With the advent of powerful new telescopes on the ground and in space, planetary astronomy has gone though an exciting development over the past decade and we are bound to find many more dwarf planets in future, if we continue placing them all in the list of 'Planets', in the company of Earth moon then we'll doing injustice to this elite club members having such distinctive features as life, air, water, atmosphere etc.
Astronomy, the branch of physics studying celestial bodies, gives room for improvements and evolutions with newer discoveries. ...