Ophiuchus The constellation of Ophiuchus is named from the Greek for Serpent-Bearer. The serpent is represented by the constellation of Serpens, which wraps around the back of Ophiuchus. Hold your mouse cursor over the image to see constellation figures, boundaries, and star identifications. Alpha Ophiuchi is Rasalhague, the brightest star in the constellation. It has an apparent visual magnitude of 2.08. Its name means the "Head of the Serpent-Bearer." Rasalhague is an spectral-type A giant star that is located 48 light-years away. Ophiuchus lies north of the galactic center in Sagittarius, and large dark nebulae in the southern part of the constellation obscure part of the central bulge of the galactic core. These dark nebulae include the Dark Horse and Rider, and the Pipe Nebula area near Theta Ophiuchi. A very large emission nebula, Sh2-27, surrounds the star Zeta Ophiuchi, and reflection nebula IC 4604 surrounds Rho Ophiuchi and is part of the amazing Rho Ophiuchi - Antares nebulae complex. Many Barnard dark nebulae are located between Antares and M8, the Lagoon Nebula, in Sagittarius. Barnard's Star is also located in Ophiuchus. It is a 9.54 magnitude red dwarf that is only 5.98 light-years away, the fourth closest star to our Sun after the three stars in the Alpha Centauri system. Barnard's star is the closest star that can be seen from the northern hemisphere. It was discovered by E. E. Barnard, who measured its proper motion (10.3 arcseconds per year) in 1916. Yed Posterior (Delta Ophiuchi), at magnitude 2.73, and Yed Prior (Epsilon Ophiuchi) at magnitude 3.23, are two stars of reasonably similar brightness 1.5 degrees apart that mark the Serpent-Bearer's left arm which holds the head of the Serpent (Serpens Caput). Ophiuchus contains a number of globular clusters such as Messier 9, Messier 10, Messier 12, Messier 14, Messier 19, Messier 62 and Messier 107, as well as some interesting planetary nebula including the Twin Jet Nebula, M2-9, and the Little Ghost Nebula, NGC 6369. The Sun is located in the constellation of Ophiuchus from November 29 to December 18. Ophiuchus was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 11th largest of today's 88 modern constellations, covering 948 square degrees of sky. Serpens Serpens, the Serpent, is the only constellation that is split into two separate parts. Serpens Caput, the Serpent's Head, is the western portion, and Serpens Cauda, the Serpent's Tail, is the eastern part. Ophiuchus, the Serpent Bearer, lies between Serpens Caput and Serpens Cauda. Serpens is a very old constellation that dates back to Babylonian times. Alpha Serpentis is Unukalhai, the "Serpent's Neck." It is also sometimes called Cor Serpentis, the "Serpent's Heart." It is the brightest star in the constellation, located in Serpens Caput, at an apparent magnitude of 2.63. It is a spectral-class K orange-giant star that is located 73 light-years away. Unukalhai is also a double star. The primary is magnitude 2.65 and the secondary is magnitude 11.8. They are separated by 58 arcseconds. Serpens contains two Messier objects: globular cluster Messier 5 and the cluster / nebula complex Messier 16, the Eagle Nebula. Serpens was cataloged by the Greek astronomer Ptolemy in the second century C.E. (Common Era). It is the 23rd largest of today's 88 modern constellations, covering 637 square degrees of sky. North is to the top left in the above image.
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