"Pluto was found really close to where Lowell thought a planet should be ... you have this third zone of icy dwarf planets, ...

Pluto was once called the ninth planet, but in 2006, scientists changed its status to a dwarf planet. A planet must clear its orbit of other objects, but Pluto shares its space with many small icy ...

For decades, it has consisted of nine planets, even as scientists debated whether Pluto really belonged ... as “2003 UB313” become the 10th planet? Should Pluto be demoted?