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
Sailor Pluto doesn't display any personality traits associated with Scorpios despite being born under the sign; it seems to have been picked solely for its astrological significance. Also, according to Naoko Takeuchi's notes in the various artbooks, she mentions that "Setsuna wears hotpants as well at home, but basically she also likes long skirts" and that she believes "Setsuna should forever wear white clothes". The kanji of Setsuna's surname translates as and . Together, they constitute most of the name of the dwarf planet Pluto in Japanese: . Her given name is in hiragana and so its meaning is not inherent, but