Object Analysis

Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It was the first and the largest Kuiper belt object to be discovered. After Pluto was discovered in 1930, it was declared to be the ninth planet from the Sun. Beginning in the 1990s, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt.

In 2006, the International Astronomical Union (IAU) formally re-defined the term planet, excluding Pluto and reclassifying it as a dwarf planet. Pluto is composed primarily of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume.

The New Horizons spacecraft performed a flyby of Pluto in July 2015, becoming the first and, to date, only spacecraft to do so. It captured stunning images of a complex world with mountains of water ice, vast plains of nitrogen ice (Sputnik Planitia), and a tenuous blue atmosphere.