Serpens is a unique constellation in the northern celestial hemisphere, distinct because it is the only one divided into two separate parts: Serpens Caput (the Serpent's Head) and Serpens Cauda (the Serpent's Tail). These two parts are separated by the constellation Ophiuchus, the Serpent Bearer, which appears to be holding the serpent. Serpens is not a large constellation, but its distinctive shape and position make it a fascinating subject for stargazers.
Key Features
Serpens is unique in that it is split into two distinct sections, Serpens Caput and Serpens Cauda, which lie on either side of Ophiuchus. This division is rare among constellations and adds to its interest. The constellation contains several notable deep-sky objects, including the Eagle Nebula (M16), home to the famous "Pillars of Creation" photographed by the Hubble Space Telescope.
Mythology
In Greek mythology, Serpens is often associated with the myth of Asclepius, the god of medicine. Asclepius is said to have learned the secrets of immortality by observing a serpent bring another serpent back to life with a herb. Zeus, fearing that humans might attain immortality, struck Asclepius down with a thunderbolt. Ophiuchus, representing Asclepius, is depicted holding the serpent, symbolizing his knowledge of life and death. The constellation's division into two parts may represent the dual nature of the serpent in mythology: life-giving and deadly.
Notable Stars
The brightest star in Serpens Caput is Unukalhai (Alpha Serpentis), a giant star with a slight orange hue, located about 73 light-years from Earth. In Serpens Cauda, the brightest star is Alya (Theta Serpentis), a white binary star system. Other notable stars include Beta Serpentis, a white star in Serpens Caput, and Delta Serpentis, another binary system.
Visibility
Serpens is best viewed during the summer months in the Northern Hemisphere, particularly in July. Its two parts, Serpens Caput and Serpens Cauda, are visible from latitudes between +80° and -80°, making it accessible to observers in most parts of the world. Serpens Caput can be found to the west of Ophiuchus, while Serpens Cauda lies to the east.
Tips for Observing
To observe Serpens, find a dark sky location away from city lights. Start by locating Ophiuchus, a large constellation near the bright star Antares in Scorpius. Serpens Caput lies to the west of Ophiuchus, while Serpens Cauda is to the east. Binoculars or a small telescope can help bring out the details of Serpens' stars, and a telescope is essential for viewing deep-sky objects like the Eagle Nebula. Observers should note the contrast between the two halves of Serpens and how they interact with the constellation Ophiuchus.