Question

What led to a change in the number of officially classified planets in 2006? Scientists determined that some inner planets are too small to be considered spherical. Scientists determined that Pluto does not orbit a star. Scientists determined that the dwarf planet Eris should be included. Scientists determined that Pluto does not clear its orbit of other objects.

Answer 1

The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet.