Ophiuchus

Ophiuchus (abbreviation: Oph), the Serpent-Bearer, the mythical healer Aesculapius (his snaked-entwined staff, the caduceus, is the physician's symbol), is a large constellation, in the shape of a huge rough pentagon, mostly of the southern hemisphere, south of Hercules and west of Serpens (Caput). It is replete with bright globular clusters. See below for details of the constellation's brightest stars and interesting deep sky objects.

Snake Nebula

Snake Nebula Canada-France-Hawaii Telescope.

The Snake Nebula (Barnard 72) , also known as Barnard's Dark S Nebula, is a distinctively shaped dark nebula in the constellation Ophiuchus, 1.5° north-northeast of Theta Ophiuchi (RA 17h 23m, Dec –23° 38'); it was first catalogued by Edward Barnard. To its right is B68, an extremely dense dark nebula, and below it are B69, B70, and B74.

Kepler's Star

Kepler's Supernova Remnant. Image: Hubble Space Telescope.

Kepler's Star (SN Oph 1604) was a Type Ia supernova whose light reached Earth in 1604. The resulting "new" star, which reached a visual magnitude of about –2.2 in late October, was described by Johannes Kepler in his De Stella Nova (1606). The visible supernova remnant consists of a few faint filaments and knots in the galactic halo at a distance of 30,000 to 40,000 light-years, and 4,000 to 5,000 light-years above the galactic plane. Also known as Kepler's Supernova.

Stars brighter than magnitude 4.0
star	vis mag	abs mag	spec type	distance (ly)	RA (h m s)	Dec (° ' ")
Alpha (Rasalhague)	2.08	1.30	A5III	47	17 34 56	+12 33 36
Eta (Sabik)	2.43	0.37	A2V	84	17 10 23	-15 43 30
Zeta (Han)	2.54	-3.20	O9.5Vn	458	16 37 09	-10 34 02
Delta (Yed Prior)	2.73	-0.86	M0.5III	170	16 14 21	-03 41 39
Beta (Cebelrai)	2.76	0.76	K2III	82	17 43 28	+04 34 02
Kappa	3.19	1.08	K2III	86	16 57 40	+09 22 30
Epsilon (Yed Posterior)	3.23	0.64	G9.5IIIbCN	108	16 18 19	-04 41 33
Theta	3.27	-2.92	B2IV	563	17 22 00	-24 59 58
Nu	3.32	-0.04	K0IIIaCN	153	17 59 01	-09 46 25
72	3.71	1.68	A4IVs	83	18 07 21	+09 33 50
Gamma	3.75	1.43	A0V	95	17 47 53	+02 42 26
Lambda (Marfik)	3.82	0.28	A0V+A4V	166	16 30 55	+01 59 02
67	3.93	-4.26	B5Ib	1,420	18 00 39	+02 55 53

Other objects of interest
name	type of object	notes
Barnard's Star	star	See main entry
Rho Oph	star	A multiple star, N of Antares. Small telescopes reveal two B stars of magnitude 5.02 and 5.92, each with an eighth magnitude companion. These four stars form a V-shaped group. Rho Oph itself is embedded in a nebulosity, IC 4604
NGC 6572	planetary nebula	A bright oval disk that makes a good target for small telescopes at high magnification. Magnitude 9.0; diameter 11'; RA 18h 12.1m, Dec +06° 51.4'
IC 4665	open cluster	In the same field as Beta Oph, binoculars show about 20 stars of seventh magnitude and fainter stars scattered over an area of about 1°. Magnitude 4.2; diameter 41'; RA 17h 46.3m, Dec +05° 43'
NGC 6633	open cluster	More than 60 members. Magnitude 4.6; diameter 27'; RA 18h 27.7m, Dec +06° 34'
M9 (NGC 6333)	globular cluster	Magnitude 7.9; diameter 9.3'; distance 5,500 light-years; RA 17h 19.2m, Dec -18° 31'
M10 (NGC 6254)	globular cluster	Together with M12, the most prominent of the globulars in Ophiuchus. Both are visible to the naked eye. Binoculars or a small telescope show them as misty patches. Magnitude 6.6; diameter 15.1'; RA 16h 57.1m, Dec -04° 06'
M12 (NGC 6218)	globular cluster	Slightly larger but fainter than M10. Magnitude 6.6; diameter 14.5'; RA 16h 47.2m, Dec -01° 57'
M14 (NGC 6402)	globular cluster	A less condensed center with a slightly elliptical shape. Magnitude 7.6; diameter 11.7'; RA 17h 37.6m Dec -03° 15'
M19 (NGC 6273)	globular cluster	The most oblate known globular cluster. Magnitude 7.1; distance: 27,000 light-years; RA 17h 02.6m, Dec -26° 16'
M62 (NGC 6266)	globular cluster	The most irregularly-shaped known globular cluster. Magnitude 6.6; diameter 14.1; RA 17h 01.2m, Dec -30° 07'
M107 (NGC 6171)	globular cluster	Smaller and fainter than M 10 or M12 and, unusually for globulars, contains dark regions. Magnitude 8.1; diameter 10.0'; RA 16h 32.5m, Dec +03° 13'