Pluto is the second-largest of the dwarf planets in the Solar System and the tenth-largest body with a direct orbit around the Sun. It was discovered in 1930 by American astronomer Clyde W. Tombaugh and was named by 11-year-old English schoolgirl Venetia Phair.

Although it was originally considered one of the major planets of the Solar System, Pluto has been classified since 2006 as a dwarf planet. Pluto has a surface area about one-fifth the size of Earth's and a mean radius of 1,195 kilometers. It has an oval-shaped orbit that periodically brings it closer to the Sun than Neptune, which is normally closer.

Like its closest neighbors, Pluto is composed mostly of ice and rock, with more than 98% of Pluto's surface being covered in nitrogen ice. There are also traces of methane and carbon monoxide present. Beneath the surface, it is believed there is a thicker layer of water ice that rests on a core of water ice and silicate. The planet's color is light brown and yellow. Since Pluto is so far away, no photographs have been taken of it at close enough range to show surface detail.

Pluto has three moons: Charon, Nix, and Hydra. In the depiction above, Pluto is seen in the distance from the terrain of Charon. The largest moon, Charon was discovered in 1978 by American astronomer James W. Christy. It was believed to be the planet's only moon until 2005, when the Hubble Space Telescope's Pluto Companion Search Team identified Nix and Hydra.

NASA scientists expect to fly by Pluto and all three of its moons in 2015 as part of the New Horizons mission. New Horizons was launched on January 19, 2006 and passed Jupiter just over a year later. It is expected to reach Pluto in July 2015 before exiting the Solar System. Interestingly, some of the ashes of Clyde Tombaugh are confirmed to be aboard the craft, meaning the planet's discoverer will finally be able to "visit" it almost two decades after his death.

Although it has been demoted to dwarf planet status by the International Astronomical Union, people around the world still consider Pluto to be a major planet and have taken up the rather emotional cause of preserving Pluto's status. In the days after it was announced that scientists has demoted Pluto, countless petitions were created to make Pluto a "real" planet again. PlutoPetition.com has received almost 20,000 "votes" in favor of Pluto being named a planet again, and an endless number of t-shirts, novelty items, and even "stuffed planets" have been released celebrating Pluto and its huge place in the hearts of billions.