(Gengwu in the first month on the 20th), February 18, 1930, the newly discovered planet beyond Neptune was named Pluto.

1930 18, Royal Observatory Colette Dhoop discovered the ninth planet of the solar system. One proposed by the British girl named "Pluto" target = "_blank"> Pluto, it is the last one discovered planet of the solar system. Orbital period 249 the years.
Ground observation, Pluto's surface is covered forward to solid methane, it has a thin layer of the atmosphere. gradually away from the sun to Pluto, the thin layer of gas will gradually solidified surface. (the L $ dj��.c��m) NASA plans to launch in 2001 to Pluto spacecraft, so the scientists were able to solidify its atmospheric former study this distant planet. (history www.lssdjt.com) In in 1978 found that Pluto has a satellite (Charon) the satellite's surface seems different with Pluto, its surface is covered with ice seems solid methane more. (lsjt.org) it fixed orbit Pluto's gravity, so they both always relative to the same hemisphere.
no spacecraft has visited Pluto, so it still remain a mystery planet because of the distance of Pluto and the sun is so far away, resulting in its surface temperature is almost close to minus 240 degrees Celsius.
in 2006 out of the solar system, nine giant planets outside.