What major classification was Pluto given in 2006?

In 2006, Pluto was reclassified as a "dwarf planet" by the International Astronomical Union (IAU). This decision stemmed from the recognition that while Pluto orbits the Sun and has sufficient mass for its self-gravity to assume a nearly round shape, it does not fulfill all the criteria necessary to be considered a full planet. Specifically, it does not clear its neighboring region of other debris—one of the defining characteristics of a planet.

The reclassification of Pluto has significant implications for our understanding of the solar system. It highlights the distinctions between the larger planets and smaller celestial bodies, which can include objects like Pluto that share certain characteristics with planets but do not meet the criteria for classification as such. This change also reflects ongoing developments in astronomy as our knowledge of celestial bodies expands and evolves. Dwarf planets, including Pluto, are recognized as an important category of objects within the solar system, contributing to the complexity and diversity of celestial mechanics.