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Ophiuchus is a large constellation located around the celestial equator. Its name is from the Greek "serpent-bearer", and it is commonly represented as a man grasping the snake that is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. It was formerly referred to as Serpentarius and ''Anguitenens''. ==Location== Ophiuchus is located between Aquila, Serpens and Hercules, northwest of the center of the Milky Way. The southern part lies between Scorpius to the west and Sagittarius to the east. In the northern hemisphere, it is best visible in summer. It is located opposite Orion in the sky. Ophiuchus is depicted as a man grasping a serpent; the interposition of his body divides the snake constellation Serpens into two parts, Serpens Caput and Serpens Cauda, which are nonetheless counted as one constellation. Ophiuchus straddles the equator but lies predominately to its south. However, Rasalhague, a fairly conspicuous star in its north, is circumpolar north of 78° north latitude. The constellation extends southward to −30° declination. Segments of the ecliptic that lie within Ophiuchus lie south of −20° declination. A determination of exactly where these stars are visible on Earth would depend on atmospheric refraction, the Novaya Zemlya effect, mountains and clouds. In contrast to Orion, it is in the period November–January (summer in the Southern Hemisphere, winter in the Northern Hemisphere) when Ophiuchus is in the daytime sky and thus not visible at most latitudes. However for much of the Arctic Circle in the Northern Hemisphere's winter months, the Sun is below the horizon even at midday. Stars (and thus parts of Ophiuchus, especially Rasalhague) are then visible at twilight for a few hours around local noon, low in the South. In the Northern Hemisphere's spring and summer months, when Ophiuchus is normally visible in the night sky, the constellation is actually not visible, at those times and places in the Arctic when midnight sun obscures the stars. In countries close to the equator Ophiuchus appears overhead in June around midnight and in the October evening sky. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ophiuchus」の詳細全文を読む スポンサード リンク
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