Pluto in size of Charon and Pluto has prompted some astronomers to call it a double dwarf planet. The system is also unusual among planetary systems in that each is tidally locked to the other, which means that Pluto and Charon always have the same hemisphere facing each other. From any position on either body, the other is always at the same position in the sky, or always obscured. This also means that the rotation period of each is equal to the time it takes the entire system to rotate around its barycenter. In 2007, observations by the Gemini Observatory of
Definition of planet IAU General Assembly meeting in Prague in August 2006, and on August 24, the IAU put a final draft to a vote, which combined elements from two of the three proposals. It essentially created a medial classification between "planet" and "rock" (or, in the new parlance, "small Solar System body"), called "dwarf planet" and placed Pluto in it, along with Ceres and Eris. The vote was passed, with 424 astronomers taking part in the ballot. The IAU also resolved that ""planets" and "dwarf planets" are two distinct classes of objects", meaning that dwarf planets, despite their name, would not be