Serpens, or the Serpent, is held by the Serpent Holder,
Ophiuchus, and is the only constellation
to consist of two separate parts - Serpens Caput (the
Head) and Serpens
Cauda (the Tail).
Though the stars of this region have been seen as a serpent for thousands of
years, their symbolic meaning remains uncertain. It is thought likely that the Serpent and its bearer
Ophiuchus are related to the Greek healer-god Asclepius. The
Greeks believed that the serpents of Asclepius could cure diseases, and so belong a long association between
serpents and medicine that continues to our own time.
The stars of Serpens form the shape of a long writhing snake that starts near the Northern Crown,
passes southward through Serpens Caput, then through the body of
Ophiuchus. When the shape emerges into Serpens
Cauda, it turns northward again, and carries on to reach its end into the Milky Way.
The tip of the Serpent's nose is the faint star Rho Serpentis, while the tip of its tail is marked by the
similarly faint Alya. A number of the stars
that form part of the Serpent's body actually belong to the constellation
Ophiuchus. Yed Prior,
Yed Posterior, Upsilon Ophiuchi, Zeta Ophiuchi
and Sabik are all Ophiuchan stars
that lie along the star-snake's body.
Though its shape is well-defined, Serpens is lacking in bright stars.
The brightest is Unukalhai (the 'serpent's neck') an orange
giant about seventy light years away, with a
magnitude of +2.6. Eta Serpentis, the next brightest
star, is nearly a magnitude fainter at +3.3.
Star Clusters and Nebulae
Serpens contains no deep-sky objects that are visible to the naked eye, but it is not without points
of interest. One of these is the very distant Globular Cluster M5, in the southern parts of
Serpens Caput. About 25,000 light years
away, this gigantic ball of stars is close to the Nucleus of the Milky Way Galaxy.
Much closer to Earth, at approximately 1,300 light years,
is the open cluster IC 4756. This is close
to the tip of the Serpent's Tail, in Serpens Cauda.
Also to be found within the Serpent's Tail is the well-known
nebula M16, better known as the
Eagle Nebula because it forms the shape of a flying eagle with outstretched
wings. In the heart of this nebula are three towering columns of gas and dust,
the subject of one of the Hubble Space Telescope's most famous images.