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A large constellation on the celestial equator, representing a man holding a serpent (the constellation Serpens). It contains the second-closest star to the Sun, Barnard's Star. Although Ophiuchus is not officially a constellation of the zodiac, the Sun nevertheless passes through it in the first half of December. Its brightest star is Rasalhague (Alpha Ophiuchi). Rho Ophiuchi is a quadruple star of magnitudes 5.0, 5.7, 6.7, and 7.3, surrounded by the faint Rho Ophiuchi Nebula. 70 Ophiuchi is a double star with an orbital period of 88 years, magnitudes 4.2 and 6.0, colours yellow and orange, 16 l.y. away. RS Ophiuchi is a recurrent nova that has flared up to naked-eye brightness six times, in 1898, 1933, 1958, 1967, 1985, and 2006. NGC 6633 and IC 4665 are large open clusters. Ophiuchus contains numerous globular clusters, including M9, M10, M12, M14, M19, M62, and M107.

Subjects: Astronomy and Astrophysics.

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