Since its discovery in 1930 , Pluto has been the subject of debates about the true nature of the planet or not. Always been considered as the smallest planet in the solar system , it is also smallest of our moon.
The latest astronomical discoveries have highlighted the existence of an entire asteroid belt beyond the solar system. This discovery which established once and for all the de-classification of Pluto from planet to asteroid. In fact asteroids have been discovered even larger than Pluto. The source of contention was the discovery of 2003 UB313 which was given the name of the planet Xena (from the greek foreign ), 10 planet of the solar system , as at the time of its discovery, Pluto was still considered a planet. Others took instead this discovery as the reason for which it was necessary to reclassify Pluto as an asteroid and no more planet.
This last vision was enshrined in Prague from the International Astronomical Union (IAU), which specified a precise definition to classify a planet in the astral body :
“The planets of the solar system 8 are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. There are also a number of Dwarf Planets. To these belong Pluto, 2003 UB313 and Ceres which is between Mars and Jupiter. The other celestial bodies that revolve around the sun, such as asteroids and comets, are now defined as a Small solar system body“
Pluto is then incorporated into the asteroid belt outside the solar system, and declassified by the planet. The solar system is therefore composed of eight planets and no more nine.