Serpens

Serpens (abbreviation Ser), the Serpent, wrapped around Ophiuchus, the Serpent Bearer, is a faint constellation of the northern hemisphere. It is unique in being the only constellation split into two parts, neither of which touches the other. Entwined around and separated by Ophiuchus, Serpens Caput (the Serpent's Head) is the western portion and Serpens Cauda (the Tail) the eastern portion. The Greek letter names of the constellation's main stars are distributed between the two portions: Alpha through Epsilon in Serpens Caput, Zeta and onward in Serpens Cauda.

Serpens contains the diffuse nebula M16 (NGC 6611) and a sixth magnitude open cluster embedded in the Eagle Nebula (diameter 35 × 28 arcminutes; RA 18h 18.8m, Dec –13° 47'). Among its other interesting deep sky objects are the globular clusters known as M5 (NGC 5904) (magnitude 5.8; diameter 17.4'; RA 15h 18.6m, Dec +02° 05') and the Serpens Dwarf. See below for details of the constellation's brightest stars.

Serpens Dwarf

Serpens Dwarf (Palomar 4, UGC 9792) is not, as its name might suggest, a dwarf galaxy, but the second most remote globular cluster of our own Milky Way Galaxy. It lies in the remote halo in the direction of Ursa Major (RA 11h 29m 16.8s, Dec +28° 58' 25").

Stars in Serpens brighter than magnitude 4.0
star	vis mag	abs mag	spec type	distance (ly)	RA (h m s)	Dec (° ' ")
Alpha (Unukalhai)	2.63	0.87	K2IIIbCNFe	73	15 44 16	+06 25 32
Eta (Alava)	3.23	1.84	K0III	62	18 21 18	-02 53 56
Theta (Alya)	3.4			132	18 56 14	+04 12 10
Theta¹	4.62	1.58	A5V
Theta²	4.98	1.94	A5Vn
Mu	3.54	0.14	A0V	156	15 49 37	-03 25 49
Xi	3.54	0.99	F0III	105	17 37 35	-15 23 55
Beta (Chow)	3.65	0.29	A3V	153	15 46 11	+15 25 18
Epsilon	3.71	2.04	A2Vm	70	15 50 49	+04 28 40
Delta (Tsin)	3.80	-0.25	F0IV	210	15 34 48	+10 32 21
Gamma	3.85	3.62	F6V	36	15 56 27	+15 39 42