Serpens the Serpent Constellation Is the Only Two Part Constellation

Summary: Serpens the Serpent Constellation is the only two part constellation, with head and tail at opposite sides of Ophiuchus the Serpent Holder constellation.

Ophiuchus the Serpent Holder with Serpens, the only two part constellation, as depicted in Alexander Jamieson’s A Celestial Atlas (1822), Plate IX: Public Domain, via U.S. Naval Observatory

Serpens the Serpent Constellation is the only two part constellation, with the Serpens Caput (Serpent’s Head) and Serpens Cauda (Serpent’s Tail) disconnected by the intervening constellation of Ophiuchus the Serpent Holder.

In front view depictions of the Serpent Holder, he grasps the Serpent’s upper body, known as Serpens Caput, in his left hand. Ophiuchus’s right hand holds the Serpent’s lower body, known as Serpens Cauda.

Back view depictions of Ophiuchus reverse the grasps. With his back toward stargazers, the Serpent Holder grasps Serpens Caput in his right hand while his left hand clasps Serpens Cauda.

At mid-northern latitudes in May, Serpens the Serpent constellation rises well above the southeastern horizon around midnight. Dark skies, undisturbed by light pollution, reveal the Milky Way dip that the lowest coil of Serpens Cauda shares with Ophiuchus. Serpens Caput never nears the solar system’s hazy band of multitudinous lights.

Serpens Caput angles upward, above Libra the Scales constellation and below Corona Borealis the Northern Crown constellation. Along with Ophiuchus, Hercules the Kneeling Hero defines Serpens Caput’s eastern borders. Virgo the Maiden constellation and Boötes the Herdsman constellation frame Serpens Caput’s western boundaries.

Serpens Caput resides primarily in the northern celestial hemisphere. The constellation’s lowest expanses venture across the celestial equator, the imaginary circle projected from Earth’s equator outward into space, and dip, by a few degrees, into the southern celestial hemisphere.

In its emergence from the opposite side of the Serpent Holder, Serpens Cauda droops slightly downward toward its southern neighbor, Sagittarius the Archer constellation. Its downward trail brings Serpens Cauda closer than Serpens Caput to the plane of the ecliptic, the sun’s apparent path across the Earth-centered celestial sphere.

Often Serpens Cauda coils from behind the Serpent Holder’s left leg, as in A Celestial Atlas (1822) by Scottish rhetorician Alexander Jamieson (1782-July 1850). Prodromus Astronomiae, a posthumously published star catalog by Polish astronomer Johannes Hevelius (Jan. 28, 1611-Jan. 28, 1687), however, obscures the Serpent’s mid-section behind the front of the Serpent Holder’s body. For Hevelius, a back viewed depiction of Ophiuchus angles Serpens Caput outward from the Serpent Holder’s bent left leg and Serpens Cauda outward from the Serpent Holder’s straightened, right left.

Quickly Serpens Cauda angles upward as Ophiuchus’s grasp raises the rest of the Serpent’s lower body, all the way to its tail, aloft. Scutum the Shield constellation and Aquila the Eagle constellation mark Serpens Cauda’s eastern borders. Hercules the Kneeling Hero constellation perches above while Ophiuchus claims the Tail’s western frontier.

For about 145 years, Serpens Cauda troubled the forelegs and a hind leg of a late-18th century constellation, Poniatowski’s Bull. In 1777, Polish-Lithuanian Jesuit astronomer Marcin Odlanick Poczobutt (Oct. 30, 1728-Feb. 7, 1810) discerned and created, from unfigured stars in Ophiuchus, a small, bovine constellation honoring Stanisław II August, last King and Grand Duke of the Polish-Lithuanian Commonwealth, as a dedicated patron of arts and sciences. Poniatowski’s Bull constellation became obsolete after its exclusion from the 88 modern constellations named by the International Astronomical Union (IAU) in 1922. The small constellation, however, survives as a v-shaped asterism, Poniatowski’s Bull, near the Serpent Holder’s right shoulder.

As with Serpens Caput, Serpens Cauda straddles the celestial equator. Contrastingly, about one-third of Serpens Cauda resides in the northern celestial hemisphere while about two-thirds lie in the southern celestial hemisphere.

Serpens the Serpent constellation rates as 23rd largest among the 88 modern constellations established by the International Astronomical Union. Its total area of 636.928 square degrees places it between its eastern neighbor, Aquila the Eagle constellation, number 22 at 652.473 square degrees, and Perseus the Hero constellation, number 24 at 614.997 square degrees.

Serpens Caput claims double the area of Serpens Cauda. Serpens Caput contributes 428.484 square degrees to the total of 636.928 square degrees. Serpens Cauda covers 208.444 square degrees.

The takeaway for Serpens the Serpent constellation as the only two part constellation is that Serpens Caput (Serpent’s Head) and Serpens Cauda (Serpent’s Tail) noticeably frame Ophiuchus the Serpent Bearer for stargazers at mid-northern latitudes in May.

naked eye astronomy visibility of Serpens the Serpent, the only two part constellation:
Serpens Caput constellation (left); Serpens Cauda constellation (right): Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Ophiuchus the Serpent Holder with Serpens, the only two part constellation, as depicted in Alexander Jamieson’s A Celestial Atlas (1822), Plate IX: Public Domain, via U.S. Naval Observatory @ http://aa.usno.navy/mil/library/

naked eye astronomy visibility of Serpens the Serpent, the only two part constellation:
Serpens Caput constellation (left): Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:SerpensCaputCC.jpg
Serpens Cauda constellation (right): Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:SerpensCaudaCC.jpg

For further information:

Jamieson, Alexander. A Celestial Atlas: Comprising a Systematic Display of the Heavens in a Series of Thirty Maps Illustrated by Scientific Description of Their Contents and Accompanied by Catalogues of the Stars and Astronomical Exercises. London, England: G. & W.B. Whittaker, 1822.
Available via U.S. Naval Observatory Library @ http://aa.usno.navy.mil/library/

Kaler, James B. (Jim). "Ophiuchus and Serpens." University of Illinois Astronomy Department.
Available @ http://stars.astro.illinois.edu/sow/ophser-p.html

Plotner, Tammy. "Serpens Caput." Universe Today. Dec. 24, 2015.
Available @ http://www.universetoday.com/23586/serpens-caput/

Plotner, Tammy. "Serpens Cauda." Universe Today. Dec. 24, 2015.
Available @ http://www.universetoday.com/23601/serpens-cauda/

Ridpath, Ian. “Ophiuchus the Serpent Holder.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/ophiuchus.htm

Ridpath, Ian. “Serpens the Serpent.” Ian Ridpath > Star Tales.
Available @ http://www.ianridpath.com/startales/serpens.htm