February 4, 1906 (, Heigo In first month 11), Pluto discoverer Clyde Tombaugh was born.

1929, Lowell Observatory, invited to the Tombaugh join the ranks of the unknown planet search. A sky to search, shooting a lot of negatives for each film is carefully checked, hard, tedious work. January 21, 1930, Tombaugh finally Gemini negatives found a new planet.
Pluto is the latest discovery of a planet, since the day be found in more than 70 years ago, (L $ dj��.����T) Pluto it with the word "controversial" linked together, one because of its The discovery process is based on a false theory; Because when the quality estimates are wrong, mistakenly included in the ranks of the major planets. 1930 American astronomer Tombaugh discovered Pluto, had miscalculated the quality of Pluto that Pluto is larger than Earth, so named for the giant planets. After nearly 30 years of further observations, its diameter is only 2300 km, is even smaller than the moon. (Lssdjt.cn)
according to the resolutions of the General Assembly of the International Astronomical Union in August 24, 2006: Pluto is considered "dwarf planet in the solar system, is no longer regarded as the major planets. The solar system have the seven moons larger than Pluto (moon, Io, Europa, Ganymede, Callisto, Titan VI and Triton a). Pluto definition asteroids serial number: 134340. (Lssdjt.com)