... Pluto: The Frozen Planet . ... The Hubble Space Telescope imaged Pluto and its moon Charon in 1994. Pluto is usually the most distant planet from the Sun but because of its elliptic orbit Pluto crossed inside of Neptune's orbit in 1979 and will cross back out again in 1999. ... This picture was taken by the Voyager 2 spacecraft in 1986 - the only spacecraft ever to visit Neptune. ... This picture was snapped by the Voyager 2 spacecraft in 1986 - the only spacecraft ever to visit Uranus. ...