Serpens: The Serpent

Serpens is the only constellation in the entire sky that the map draws in two separate, disconnected pieces. A head on one side, a tail on the other, and a healer standing between them holding both halves at once.

A name split the same way the shape itself is split

Serpens is simply the Latin word for serpent, and its genitive, Serpentis, is what attaches to its one named star, Unukalhai, formally Alpha Serpentis. Like its neighbor Ophiuchus, it sits on the celestial equator rather than being purely northern or southern, and July is listed as its best month, the same month Ophiuchus reaches its own best viewing.

The only constellation drawn as two disconnected pieces

Serpens Caput, the head, sits west of Ophiuchus, and Serpens Cauda, the tail, sits east of him. Nowhere else in the official list of 88 constellations does one figure get split apart like this. It works because the shape it represents, a snake, is genuinely a single continuous body being held in the middle by someone else's hands, so the break makes sense once you know why it is there. What a constellation actually is is worth reading if that kind of boundary decision surprises you.

The split is not a leftover ambiguity from an older, sloppier era of star-mapping. It was a deliberate decision, made once, by the astronomer who drew the modern, legally fixed boundaries for all 88 constellations in the 1920s and 1930s. That mapmaker ran into Serpens as a genuine problem: a single mythological snake grasped in the middle of its own body by Ophiuchus, whose own figure occupies the space where the animal's midsection would otherwise sit. The fix was to draw the snake in two disconnected pieces, the head on one side of Ophiuchus and the tail on the other, while still counting the whole thing as a single constellation rather than two. Serpens is the only one of the 88 handled this way, and the sky's official constellation records still reflect that choice today, listing Serpens Caput and Serpens Cauda as separate chart entries while keeping both tied to the one constellation, Serpens.

One named star carries the whole shape

Unukalhai, Alpha Serpentis, is an orange giant at magnitude 2.63, marking the serpent's heart. It is the only star in Serpens with an individual name in the lore here, which means the rest of the shape is read more by its outline, stretched across two separated halves, than by any collection of bright points worth memorizing individually. A magnitude of 2.63 is respectable but not dazzling; how star brightness works is useful background if you want to know exactly how it stacks up against brighter neighbors like Rasalhague in Ophiuchus.

Why a shedding snake became a symbol of medicine

Serpens is the great snake grasped by Ophiuchus, the serpent-bearer, who is himself identified with Asclepius the healer. The snake's habit of shedding its own skin and appearing to renew itself tied it, in the ancient imagination, directly to medicine and to healing more broadly. That symbolic link is old enough and strong enough that snake imagery still shows up on medical symbols today.

The Pillars of Creation live inside this constellation's tail

Serpens Cauda, the tail half, holds the Eagle Nebula, catalogued as M16, a star-forming nebula that contains the towering dust structures known as the Pillars of Creation. Over in Serpens Caput, the head half, M5 is a large, bright globular cluster, a completely different kind of object built from old stars rather than new ones being born. Serpens also holds Hoag's Object, a rare, near-perfect ring galaxy that looks almost too symmetrical to be real.

It is worth noticing what that spread actually means: within the boundary of one split-apart constellation, you get a nursery for brand-new stars in one half and a dense, ancient cluster of old ones in the other, plus a galaxy shape rare enough that most of the sky does not have a good example of it at all. Few constellations pack that much variety into two disconnected pieces.

What this means for you tonight

Serpens is best in July, same as Ophiuchus, since the two are locked together in the same stretch of sky. Find the serpent bearer first, then look for Unukalhai off to one side; once you have it, you can trace the head toward one edge of the healer and the tail toward the other, which is the only way this particular shape actually makes sense as one animal. If you have a reasonably dark sky and something to zoom in with, the Eagle Nebula in the tail half is worth the extra few minutes it takes to track down.

Treat this constellation as a small test of whether you can hold two halves of one idea in your head at once. Serpens Caput and Serpens Cauda are not two constellations that happen to share a name; they are one snake, interrupted by whoever it is wrapped around. Once you can point to both halves on the sky map without hesitating over which is which, you have genuinely learned this shape rather than just memorized that it exists.