Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond Neptune. It was the first Kuiper belt object to be discovered.

Pluto was discovered by Clyde Tombaugh in 1930 and was originally considered to be the ninth planet from the Sun. After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt.

A blink comparator is a viewing apparatus used by astronomers to find differences between two photographs of the night sky. It permits rapidly shifting back and forth between views of each image to create the illusion of movement of any object that has changed position between photographs.

On July 29, 2005, astronomers at Caltech announced the discovery of a new trans-Neptunian object, Eris, which was believed at the time to be bigger than Pluto. This led the International Astronomical Union to define the term "planet" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet.

Pluto has five known moons.

Pluto periodically comes closer to the Sun than Neptune, but a stable orbital resonance with Neptune prevents them from colliding.

Light from the Sun takes about 5.5 hours to reach Pluto at its average distance (39.5 AU).

The dark color of Cthulhu Macula is speculated to be the result of a "tar" made of complex hydrocarbons called tholins which form from methane and nitrogen in the atmosphere interacting with ultraviolet light and cosmic rays. The region is reminiscent of a whale in shape.

The exploration of Pluto began with the arrival of the New Horizons probe in July 2015. During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons.

The semi-major axis of Pluto's orbit varies between about 39.3 and 39.6 au with a period of about 19,951 years, corresponding to an orbital period varying between 246 and 249 Earth years.