This last point is what proved to be Pluto 's demise as a planet : There are other competing objects in its orbit . IAU demoted Pluto to a dwarf planet spring . only 4 percent of the critical letters the IAU received afterward came from Mars . In spring , Illinois lawmakers restored `` full planetary status '' to Pluto . Some scientists say the International Astronomical Union 's definition of a planet does n't make sense .
IAU demoted Pluto to a dwarf planet spring . only 4 percent of the critical letters the IAU received afterward came from Mars . In spring , Illinois lawmakers restored `` full planetary status '' to Pluto . Some scientists say the International Astronomical Union 's definition of a planet does n't make sense .