Pluto was discovered by 23-year-old Clyde Tombaugh at the Lowell Observatory in Arizona in 1930.
The name Pluto, after the god of the underworld, was proposed by Venetia Burney (1918–2009), an eleven-year-old schoolgirl in Oxford, England, who was interested in classical mythology. She suggested it in a conversation with her grandfather Falconer Madan, a former librarian at the University of Oxford'sBodleian Library, who passed the name to astronomy professor Herbert Hall Turner, who cabled it to colleagues in the United States.
Between 1930 and 2006 it was classed as the Solar System's ninth planet. Its status as a major planet fell into question following further study of it and the outer Solar System over the next 75 years. Starting in 1977 with the discovery of the minor planet Chiron, numerous icy objects similar to Pluto with eccentric orbits were found.The most notable of these is the scattered disc object Eris, discovered in 2005, which is 27% more massive than Pluto.The understanding that Pluto is only one of several large icy bodies in the outer Solar System prompted the International Astronomical Union (IAU) to formally define “planet” in 2006. This definition excluded Pluto and reclassified it as a member of the new "dwarf planet" category.
Pluto has five knownmoons: Charon(the largest, with a diameter just over half that of Pluto), Nix, Hydra, Kerberos and Styx. Pluto and Charon are sometimes described as a binary system because the barycentreof their orbits does not lie within either body.The IAU has yet to formalise a definition for binary dwarf planets, and Charon is officially classified asa moon of Pluto.
On July 14, 2015, the Pluto system is due to be visited by spacecraft for the first time.The New Horizons probe will perform a flyby during which it will attempt to take detailed measurements and images of Pluto and its moons. Afterwards, the probe may visit several other objects in the Kuiper belt.
