Serpens is unique among modern constellations in that it is separated into two parts. Serpens Caput, the head, begins near Corona Borealis, and descends southward until it connects to Ophiuchus (the serpent bearer). Serpens Cauda, the tail, begins on the other side of Ophiuchus and ascends north and eastward, terminating near Aquila. Serpens is often depicted as passing behind Ophiuchus and emerging from the other side. Since Serpens is a lengthy constellation that extends primarily in an east-west direction, it reaches its highest nightfall ascension beginning in June with the head and ending with the tail in August. The entire constellation is situated for best nightfall viewing in July.
Serpens Cauda extends into the Milky Way, so there are several deep sky objects in that section. Two of these are Messier objects, M5, and M16 (the Eagle Nebula, which includes the Pillars of Creation and its associated star cluster). Hoag’s Object is a face-on example of a very rare class of galaxies known as ring galaxy.
© James R. Johnson, 2014.