Wikipedia:Today's featured article/July 14, 2015
Pluto is a dwarf planet orbiting the Sun, with about a sixth of the mass of the Moon and a third of its volume. Like other Kuiper belt objects, which are generally outside Neptune's orbit, Pluto is primarily rock and ice. It has an elongated and highly inclined orbit that takes it from 49 astronomical units (7.3 billion km) away from the Sun down to 30, closer than Neptune. Light from the Sun takes about 5.5 hours to reach it at its average distance. Since its discovery in 1930, it had been considered the ninth planet, but the International Astronomical Union came up with a new definition for planets in 2006 that excluded Pluto after many other similar icy objects were found, including Chiron and Eris. Pluto has five known moons: Charon (about half as wide as Pluto), Styx, Nix, Kerberos, and Hydra. On 14 July 2015, a spacecraft is visiting the dwarf planet and its moons for the first time: the New Horizons probe is performing a flyby and attempting to take detailed measurements and images. NASA has invited the general public to suggest names for surface features that will be discovered on Pluto and Charon. (Full article...)
Part of the Dwarf planets featured topic.