Why Pluto is not a planet?
•  Pluto was first discovered by Clyde Tombaugh in 1930
• The redefinition of the planet by the IAU on 24th August 2006 states that the solar system  Planet is a celestial body. The association delivers three basic rule for planets.
1. It is in orbit around the sun.
2. It has sufficient mass so that it assumes a hydrostatic equilibrium shape (nearly sphere)
3. Its orbit does not interrupt the neighbour planets
• A  non-satellite planet pluto obeys the first two rules but it does not fulfil the third rule so it considers as a dwarf planet.