Constellation Serpens (Serpent)

Serpens: IAU Constellation Map [150]


The constellation consists of two parts separated by Ophiuchus. In the west is the more conspicuous part of Serpentis Caput and in the east Serpentis Cauda. Both parts are south of Hercules, or Corona Borealis. The head of the snake forms a small equilateral triangle at the northern end of a slightly wavy line that symbolizes the body. The total area of the two partial constellations is 637 square degrees. The snake head culminates around midnight on May 17th and the snake tail around June 21st. [9, 15]

Stars with Proper Names [154]
α Ser Unukalhai, Unuk Al Hay, Unuk Elhaia, Unuk, Unukalhay, Cor Serpentis
θ1 Ser Alya, Alga
Data for constellation Serpens [150]
IAU NameSerpens
IAU GenitiveSerpentis
IAU Abbr.Ser
English NameSerpent
Opposition17 May
Season (47° N)March … September
Right Ascension15h 10m 25s … 18h 58m 18s
Declination-16° 08' 24" … +25° 39' 51"
Area637 deg2
Neighbours (N↻)CrB, Boo, Vir, Lib, Oph, Her, Sgr, Sct, Aql

Deep-Sky Object Descriptions


Constellation Serpents
Constellation Serpents: Illustration from «Uranometria» by Johann Bayer, copper engraving by Alexander Mair, 1603 [28]

Mythology and History

Serpens (Caput) and Serpens (Cauda) is an ancient constellation that depicts a serpent wrapped around the Serpent Bearer. According to Greek mythology, the snake is said to have brought Asklepios (symbolized in the Serpent Bearer) a miracle herb that heals the sick and raises the dead. [10]

Snakes have long been considered a source of healing - a concept that has consistently been a leading tenet in medical quackery in the form of "snake oil elixirs" and the like. On the other hand, Asklepios' snake became the Caduceus, the universal emblem of medicine with one or two snakes twisting around a staff.

The correct Latin spelling of the two partial constellations without brackets is Serpentis Caput (head of the snake) and Serpentis Cauda (tail of the snake), but most of the time they are ignored. [221]


  • [9] «Drehbare Sternkarte SIRIUS» von H. Suter-Haug; Hallwag-Verlag, Bern
  • [10] «dtv-Atlas zur Astronomie» von Joachim Herrmann; Deutscher Taschenbuch Verlag; ISBN 3-423-03006-2
  • [15] «Hartung's Astronomical Objects for Southern Telescopes» by David Malin and David J. Frew; Melbourne University Press 1995; ISBN 0-522-84553-3
  • [28] «Uranometria omnium asterismorum continens schemata, nova methodo delineata aereis laminis expressa» Johann Bayer, Augsburg, 1603; DOI:10.3931/e-rara-309
  • [150] IAU: The Constellations, 11. Oktober 2020;
  • [154] Yale Bright Star Catalog, 15. Oktober 2020;
  • [221] NGC 2264 and the Christmas Tree cluster; (2021-01-08)