This year marks the 75th anniversary of the discovery of Pluto. Clyde Tombaugh discovered the ninth planet in the solar system on the afternoon of Feb. 18, 1930 while he meticulously examined a pair of photographic plates he had exposed in January at Lowell Observatory. The official announcement was made on March 13. This most renegade of all the planets has been an odd, mysterious world ever since. It will remain so for at least another decade, until the yet to be launched New Horizons Pluto-Kuiper Belt Mission arrives at Pluto, the last planet in our solar system to be visited by a spacecraft. New Horizons is scheduled to launch in January 2006, and is due to swing past Jupiter for a gravity boost and scientific studies in February 2007, before finally reaching Pluto and its moon, Charon, in July 2015.
A rather interesting astronomical issue has surfaced in recent years as to whether Pluto should legitimately be included in the roster of nine major planets. It's decidedly small size makes it considerably smaller than any other planet, even smaller than several planetary satellites. In addition, it has a moon (Charon) that is more than half its size, as well as a most unplanetary, asteroid like orbit. For some time people have suggested that Pluto is really an escaped satellite of Neptune. Other's have proposed that Pluto should not be considered a planet, but rather as the "King of the Kuiper Belt Objects", a ring of a few hundred chunks of ice, strung like a dirty diamond necklace in the vastness of space beyond Neptune.