Located in the northern hemisphere, Serpens was listed amongst Ptolemy in his 2nd century listing. Serpns is unique among the modern constellations, as it is split into 2 non-contiguous parts, Serpens Caput to the west and Serpens Cauda to the east.

Between these 2 constellations lies the constellation of Ophiuchus, the “Serpent-Bearer”. In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between Mu Serpentis in Serpens Caput and Nu Serpentis in Serpens Cauda. The entire constellation covers a total of 636.9 square degrees, it ranks 23rd of the 88 constellations in size. It appears prominently in both the northern and southern skies during the Northern Hemisphere’s summer. There are 108 stars in the constellation that are brighter than magnitude 6.5, the traditional limit for naked-eye visibility.

Part of the Milky Way galactic plane passes through Serpens Cauda, which is therefore rich in galactic deep-sky objects, such as the Eagle Nebula and its associated star cluster Messier 16.

	Applicable Information
Visibility In Pacific Northwest	April to September
Best Times To View	June and July
Right Ascension	Serpens Caput:  15h 10.4m to  16h 22.5m Serpens Cauda:  17h 16.9m to  18h 58.3m
Declination	Serpens Caput: 25.66° to −03.72° Serpens Cauda: 06.42° to −16.14°
Area	Serpens Caput: 428 sq. deg. Serpens Cauda: 208 sq. deg. Total: 637 sq. deg.
Main Stars	11
Brightest Object	α Ser
Meteor showers	0
Messier objects	2
Neighboring Constellations	S. Caput: Corona Borealis Boötes Virgo Libra Ophiuchus Hercules S. Cauda: Aquila Ophiuchus Sagittarius Scutum

The Name

In Greek mythology, the constellation represents a snake held by the healer Asclepius. Represented in the sky by the constellation Ophiuchus, Asclepius once killed a snake, but it was subsequently resurrected after a second snake placed a revival herb on it before its death. As snakes shed their skin every year, they were known as the symbol of rebirth in ancient Greek society, and legend says Asclepius would revive dead humans using the same technique he witnessed.

Chinese astronomy has most of the stars that represented part of a wall surrounding a marketplace, which was in Ophiuchus and part of Hercules. Serpens also contains a few Chinese constellations.

Stars

There are several stars brighter than magnitude 4, with the brightest star in Serpens being Unukalhai, which has a visual magnitude of 2.63. The second brightest star is Eta Serpentis with a magnitude of 3.26.

The two Messier objects in these constellations are Messier 5 and Messier 16. M5 is a globular cluster that under extremely good conditions would be visible to the naked eye as a faint “star.” Binoculars or small telescopes will identify the M5 as non-stellar while larger telescopes will show some individual stars, of which the brightest are of apparent magnitude 12.2. M16 is known as the Eagle Nebula s Messier 16 and the NGC 6611 is an open cluster of stars famous for its star forming regions.

Hoag’s Object is a ring galaxies with an outer ring largely composed of young blue stars and a core made up of older yellow stars.

Other deep-sky objects in this constellation include the Blinking Galaxy or NGC 6118, spiral galaxy NGC 6118, the Serpens South Star Cluster, and the Red Square Nebula. These dim objects can only be seen in large telescopes.

Make sure to check out other articles on the site, including a brief introduction to constellations, other constellation articles, and more! Here is another resource for more information.