Pluto

Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and apparently even glaciers. Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery that many similar, intriguing worlds inhabit the distant region beyond Neptune known as the Kuiper Belt, icy Pluto was reclassified as a dwarf planet.

NASA's New Horizons was the first spacecraft to explore Pluto up close, flying by the dwarf planet and its moons in 2015.

Pluto is named after the Roman god of the underworld. It is the only planet named by an 11-year-old girl.

When Pluto was reclassified in 2006 from a planet to a dwarf planet, there was widespread outrage on behalf of the demoted planet. As the textbooks were updated, the internet spawned memes with Pluto going through a range of emotions, from anger to loneliness. But since the release of New Horizons images showing a very prominent heart-shaped feature on the surface, the sad Pluto meme has given way to a very content, loving Pluto that would like to once again be visited by a spacecraft.

The Disney cartoon character Pluto, Mickey's faithful dog, made his debut in 1930, the same year Clyde Tombaugh, an astronomer at the Lowell Observatory in Flagstaff, Arizona, discovered the dwarf planet. There is speculation that Walt Disney named the animated dog after the recently discovered planet to capitalize on its popularity, but other accounts are less certain of a direct link.