Abbreviation: Ser

Genitive: Serpentis

English: The Serpent

Size Ranking: 23rd

Area: 637 square degrees

Fully Visible: 74°N – 64°S

Serpens, follows on from Ophiuchus. Serpens is an ancient constellation, depicting a serpent or snake wound around the body of Ophiuchus, who holds the serpent’s head in his left hand and its tail in his right hand. Serpens is unique in that it is split into two separate halves either side of Ophiuchus: Serpens Caput, the head, which is the larger and more prominent half; and Serpens Cauda, the tail. Both halves taken conjointly count as one constellation.

Serpens is located via Ophiuchus.

Features of Interest:

αSer, named Unukalhai, ‘the serpent’s neck’, is an orange giant star of magnitude 2.6 and is 73 ly away.

βSer, 153 ly distant, is a blue – white main – sequence star, situated in the serpent’s head. It is of magnitude 3.7 and has a companion, magnitude 9.9, separation 30.6”, PA 265°. An unrelated background star, 29 Ser, magnitude 6.7, lies just to the north.

γSer, is white main – sequence star, magnitude 3.8 and 36 ly away.

δSer, 210 ly away, is a white star of magnitude 4.2 with a close companion, magnitude 5.2, separation 4.4”, PA 177°. This is a binary double with a period of 3168 yrs.

ηSer, magnitude 3.2, is an orange giant star 62 ly away.

θSer, named Allay, is a elegant pair of white stars of magnitudes 4.6 and 5.0, separation 22.3”, PA 104°.

They are 132 ly distant.

νSer, 193 ly away, is a blue white star of magnitude 4.3 with a wide companion, magnitude 8.3, separation 46.3”, PA 028°.

τ¹Ser, 920 ly distant, is a giant red star of magnitude 5.2 and is the brightest member of a loose scattering of eight stars of 6th magnitude near βSer. All are visible through appropriate binoculars.

R Ser, is a red giant star of the Mira type, ranging between magnitudes 5.2 and 4.4 in approximately one year. It lies about 900 ly away.

M5 (NGC 5904), is a 6th magnitude globular cluster, 26,000 ly away. It is rated as one of the finest globulars in the northern sky, second only to the famous M13 in Hercules. A telescope of 200 mm aperture will reveal its brilliant condensed centre and mottled outer regions with curving chains of stars. Close to M5, but actually in the foreground lies 5 Ser, a magnitude 5.0 yellow – white star with a magnitude 10.0 companion.

M16 (NGC6611), is a hazy – looking open star cluster, 8500 ly distant, of similar apparent size to the full Moon, embedded in the larger Eagle Nebula. The cluster is a grouping of about 60 stars of 8th magnitude and fainter. Adequate telescopes show that most of its members congregate in a V- shape in the northern half.. The surrounding Eagle Nebula adds a touch of haziness to the cluster. This area shows up beautifully in long exposure photographs.

IC4756, is a scattered open cluster of 8th magnitude stars and fainter, about two Moon diameters wide, and lies 1300 ly distant.


1. Redshift 2 – Maris Multimedia

2. The Guinness Book of Astronomy – Patrick Moore

3. Stars and Planets – Ian Ridpath and Wil Tirion

4. Sky Charts – Cartes du Ciel V 2.75.

5. Where the Stars Are – Orion..