Serpens

Serpens ("the Serpent", Greek Ὄφις) is a constellation of the northern hemisphere. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations defined by the International Astronomical Union.

It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent's Head) to the west and Serpens Cauda (Serpent's Tail) to the east. Between these two halves lies the constellation of Ophiuchus, the "Serpent-Bearer". In figurative representations, the body of the serpent is represented as passing behind Ophiuchus between μ Ser in Serpens Caput and ν Ser in Serpens Cauda. The brighest star in Serpens is Unukalhai or Cor Serpentis "Serpent's Heart", with an apparent magnitude of 2.63.

Notable features

Stars

Since Serpens is regarded as one constellation despite being split into two halves, the ordering of Bayer designations goes in order of brightness among both halves.

Only one of the stars in Serpens is brighter than third magnitude, so the constellation is not easy to perceive. α Serpentis, named Unukalhai, is in the head part. δ Serpentis, also in the head, is a double star 210 light-years from Earth. θ Serpentis. also named Alya ("the snake" in Arabic), in the tail, is also double.

Stars in the head include α, β, γ, δ, ε, ι, κ, λ, μ, π, ρ, σ, τ, χ and ω Serpentis. Stars in the tail include ζ, η, θ, ν, ξ, and ο Serpentis.

Deep-sky objects

Messier 5, a globular cluster located approximately 8° southwest of α Serpentis in the head.

Messier 16 is a young open cluster associated with the Eagle Nebula, a diffuse nebula which is a region of current star formation in the tail.

MWC 922, a nebula in the Mount Wilson Catalog, is a Symmetric Bipolar Nebula notable for its appearance as a perfectly symmetrical square or rectangle. It is also known as IRAS 18184-1302, and located at RA: 18:21:16 DEC: -13:01:27, near M16 in Serpens Cauda. The MWC is from Mount Wilson Observatory.

Part of the Milky Way passes through the tail, as illustrated by the shaded regions of the star map.

The Serpens South star cluster was uncovered by NASA's Spitzer Space Telescope in the southern portion of the Serpens cloud. The discovery was possible due to the infrared observation capabilities of the SST because at visible wavelengths the stars are completely obscured by interstellar dust in the Serpens cloud.

Hoag's Object is a perfectly shaped ring galaxy.

History

Aratus describes the constellation as follows:

Both [hands of Ophiuchus] firmly clutch the Serpent, which encircles the waist of Ophiuchus, but he, steadfast with both his feet well set, tramples a huge monster, even the Scorpion, standing upright on his eye and breast. Now the Serpent is wreathed about his two hands – a little above his right hand, but in many folds high above his left. ... Toward the Crown leans the Serpent’s jaw, but beneath his coiling form seek thou for the mighty Claws [Libra]^[1]

There were two "serpent" constellations in Babylonian astronomy, known as Mušḫuššu and Bašmu. It appears that Mušḫuššu was depicted as a hybrid of dragon, lion and bird, and loosely corresponds to Hydra. Bašmu was a horned serpent (c.f. Ningishzida) and loosely corresponds to the Ὄφις constellation of Eudoxus of Cnidus on which the Ὄφις (Serpens) of Ptolemy is based.^[2]

Namesakes

USS Serpens (AK-97) was a United States Navy Crater class cargo ship named after the constellation.

References

• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

External links

• The Deep Photographic Guide to the Constellations: Serpens
• Star Tales – Serpens
• Stellar Siblings in Serpens South

Coordinates: 17^h 00^m 00^s, +03° 00′ 00″