All scientists do not unanimously accept the latest IAU launched definition of a planet that changed the status of Pluto. They continue to view Pluto as the ninth planet. (Spinrad, 2004), (Stern, 2007)
Kuiper Belt is an unexplored region of the solar system that extends from just outside the orbit of Neptune to quite a distance from the orbit of Pluto. It is similar to the asteroid belt in that it consists chiefly of small bodies and one known dwarf planet, Pluto. But while the asteroid belt is made up of metal and hard rock, the Kuiper Belt is composed mainly of frozen objects made up of dust and ice, called KBO's. They vary in size from small clumps of ice and dust to large bodies like the Pluto. It is the revolution of these objects that determines the disc-shaped structure of the Kuiper Belt. If their orbits are interrupted in order to bring them into the inner solar system, they can be seen as comets which turn into gas and dust when they get too near to the sun. (Stern, 2007)
During the year 1905, an American astronomer named Percival Lowell, observed that some kind of gravitational force seemed to be disturbing the revolutions of Uranus and Neptune. In 1915, he postulated the existence of another planet beyond Neptune and started his research from his Arizona observatory. Unfortunately, he found his death in 1916 before he could discover Pluto.