In 2006, Pluto was declassified as a planet by the International Astronomical Union (IAU) following a vote at their 10-day General Assembly in Prague. It was given status instead as a “dwarf planet,” on account of its small size—smaller than the Moon—and highly elliptical, tilted orbit which overlaps with that of Neptune. However, only 424 of 2,700 astronomers who remained in Prague for the last day of the meeting took part. Those who voted were about only 4% of the world's 10,000 astronomers. The decision was criticized, and a petition was started. The vote established other dwarf planets: Ceres (a small body between Mars and Jupiter) and 2003 UB313 (a small body beyond Pluto, where dozens more potential dwarf planets exist). Thus Neptune became the Solar System's outermost planet, indefinitely.«Image: Pluto's surface generated from images gathered by the Hubble Space Telescope in 2002 and 2003, with extensive computer enhancement, as released by NASA on 4 Feb 2010. The Pluto Files: The Rise and Fall of America's Favorite Planet, by Neil deGrasse. - book suggestion.