Pluto's classification as a planet has been called into question.

Question

Quizplus · Accepted Answer

Pluto's classification as a planet has been debated since its discovery in 1930. In 2006, the International Astronomical Union (IAU) reclassified Pluto as a "dwarf planet." This decision was based on new definitions of what qualifies as a planet, which require a celestial body to have cleared its orbit of other debris to be considered a planet. Pluto has not cleared its orbit and therefore does not meet this requirement.

Pluto's Classification as a Planet Has Been Called into Question