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
Dwarf planet by an attempt by the IAU division III plenary session to reinstate Pluto as a planet in a second resolution. Indeed, the draft of Resolution 5A had called these median bodies "planetoids," but the plenary session voted unanimously to change the name to "dwarf planet." The second resolution, 5B, defined "dwarf planets" as a subtype of "planet", as Stern had originally intended, distinguished from the other eight that were to be called "classical planets". Under this arrangement, the twelve planets of the rejected proposal were to be preserved in a distinction between eight "classical planets" and four "dwarf planets". Resolution