Serpens Constellation Guide — Stars, the Serpent, and How to Find It
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A star-filled summer night sky — the backdrop for locating the Serpens constellation

Constellation Guide · Summer Sky

Serpens Constellation Guide — Stars, the Serpent, and How to Find the Split Constellation

Serpens is unique among the 88 constellations — it is the only one split into two disconnected halves: Serpens Caput (the Serpent's Head) and Serpens Cauda (the Serpent's Tail), with Ophiuchus the Serpent Bearer sandwiched between them. Despite this unusual division, Serpens contains spectacular deep-sky objects including the globular cluster M5 and the Eagle Nebula (M16). This guide covers everything you need to find and observe Serpens.

Brightest starUnukalhai (mag 2.6)
Unique featureSplit into two halves
Best seasonJune – August
Notable objectM5 globular cluster
By Elena Reyes Published: Updated: Reviewed & approved by Juhi Sahni, Senior Editor Editorial Standards

How to Find Serpens in the Night Sky

Serpens is unique: it exists in two separate regions of the sky, with the constellation Ophiuchus (the Serpent Bearer) dividing them. Serpens Caput (the Head) lies west of Ophiuchus, while Serpens Cauda (the Tail) lies east of it. Together, the two halves form the figure of a serpent wrapped around the Serpent Bearer's body. The brightest star, Unukalhai (Alpha Serpentis) at magnitude 2.6, marks the Serpent's neck in Serpens Caput.

The easiest way to find Serpens Caput is to locate Corona Borealis (the Northern Crown), a distinctive semicircle of stars, and look about 15 degrees south. Serpens Caput's stars form a small triangle just below Corona Borealis. To find Serpens Cauda, locate the bright star Altair in Aquila high overhead in summer and look about 20 degrees west — the Tail consists of a scattered line of faint stars stretching south of the Eagle. From mid-northern latitudes, Serpens is best visible from June through August, when Ophiuchus and its serpent are high in the southern sky during evening hours. The constellation reaches its highest point around midnight in July.

Key Stars of Serpens

StarDesignationMagnitudeDistanceNotes
UnukalhaiAlpha Serpentis2.673 lyOrange giant. "The neck of the serpent" — marks the neck.
ChowBeta Serpentis3.7153 lyWhite main sequence star in Serpens Caput.
AlyaTheta Serpentis4.0152 lyBinary star. "The fat tail" — marks the tail tip.
Eta Serpentis—3.260 lyOrange giant in Serpens Caput.
Zeta Serpentis—3.9580 lyYellow giant, near the Eagle Nebula region.

The star names of Serpens reflect its serpentine nature. Unukalhai derives from the Arabic "unuq al-hayyah," meaning "the neck of the serpent" — perfectly describing its position at the serpent's neck. Alya, the second-best-known star, comes from "alyah," meaning "the fat tail" — marking the tip of the serpent's tail in Serpens Cauda. The constellation's split nature means that its Bayer designations (Alpha, Beta, Gamma...) are spread across both halves, which can confuse first-time observers. Alpha and Beta Serpentis are in Serpens Caput, while Theta and the fainter designations are in Serpens Cauda.

The Mythology of Serpens

Serpens represents the serpent held by the healer Asclepius (the constellation Ophiuchus). In Greek mythology, Asclepius was a legendary physician who could raise the dead. The serpent, a symbol of rebirth and healing (because it sheds its skin and appears renewed), was his sacred animal. The reason Serpens is split into two halves is that the serpent is coiled around Ophiuchus's body, with its head to one side and its tail to the other — a visual representation that has been preserved in astronomical art for over 2,000 years.

The serpent as a symbol of healing and medicine has persisted into modern times — the Rod of Asclepius, featuring a serpent coiled around a staff, remains the international symbol of medicine. This ancient connection between the serpent, healing, and the stars makes Serpens one of the most culturally significant constellations in the sky, bridging ancient Greek astronomy with modern medical iconography.

Deep-Sky Objects in Serpens

Serpens straddles the Milky Way's summer branch, which means Serpens Cauda (the Tail) is rich with deep-sky objects while Serpens Caput (the Head) is dominated by the globular cluster M5 and lies outside the Milky Way's plane.

M5 — One of the Finest Globular Clusters

M5 is one of the finest globular clusters in the northern sky, ranking alongside M13 in Hercules. At magnitude 5.7, M5 is just visible to the naked eye under dark skies and a spectacular sight in any telescope. In 10×50 binoculars, it appears as a bright, round fuzzy patch. A 6-inch telescope at 100× resolves dozens of stars across the cluster's 17-arcminute face. An 8-inch scope at 150× reveals hundreds of stars gradually increasing in density toward a compressed core. M5 is approximately 24,500 light-years away and contains an estimated 500,000 stars — one of the oldest globular clusters known at 13 billion years old. It sits about 7 degrees northwest of Unukalhai, making it easy to locate.

Eagle Nebula (M16) — The Pillars of Creation

M16, the Eagle Nebula, is one of the most famous deep-sky objects thanks to the Hubble Space Telescope's "Pillars of Creation" image. Located in Serpens Cauda near the border with Scutum, M16 is a young open cluster embedded in a large emission nebula. At magnitude 6.4, the cluster is visible in binoculars, but the nebula requires an O-III or UHC filter and dark skies. A 6-inch telescope at 50× with an O-III filter shows the nebula as a faint, irregular glow surrounding a cluster of bright stars. The Pillars themselves are a challenge — they require at least a 12-inch telescope under excellent dark skies to glimpse. For a dedicated guide to this object, see our Eagle Nebula observing guide.

Omega Nebula (M17) — The Swan Nebula

M17, the Omega Nebula (also called the Swan or Horseshoe Nebula), is one of the brightest and largest emission nebulae in the summer Milky Way. At magnitude 6.0, it is visible in binoculars under dark skies. A 6-inch telescope at 60× with a nebula filter reveals its distinctive checkmark or swan-like shape spanning 15 arcminutes. The Omega Nebula is approximately 5,000 light-years away and is a star-forming region glowing from the intense ultraviolet radiation of its embedded young stars.

Observing Serpens with Binoculars

Binoculars are ideal for exploring Serpens because much of the constellation is too wide for telescope fields. A pair of 10×50 binoculars reveals M5 as a bright, fuzzy patch near Unukalhai. The Eagle Nebula star cluster is visible in binoculars, and the star fields of Serpens Cauda — lying in the Milky Way — are rich and rewarding. For binocular recommendations, see our best astronomy binoculars guide.



Observing Serpens with a Telescope

M5 is the must-see object in Serpens Caput, and it rewards every aperture from binoculars through large Dobsonians. Start at 50× to frame the cluster, then increase magnification to 100–150× to resolve individual stars. The cluster's core is dense and bright, with stars gradually thinning toward the edges. For telescope recommendations, see our best Dobsonian telescopes guide.

In Serpens Cauda, the Eagle and Omega Nebulae are the highlights. Both require nebula filters (O-III or UHC) to show their full extent. The Eagle Nebula benefits from a wide-field eyepiece at 40–50× to capture both the star cluster and the surrounding nebulosity. The Omega Nebula's distinctive checkmark shape is visible in 6-inch scopes at 60× with a filter. Both objects are embedded in the rich Milky Way star fields of summer — scanning this region with a rich-field telescope at 30× is one of the great pleasures of summer astronomy.



Frequently Asked Questions

Why is Serpens split into two parts?

Serpens is the only constellation split into two disconnected halves because the serpent is wrapped around Ophiuchus the Serpent Bearer. Serpens Caput (the Head) is west of Ophiuchus, Serpens Cauda (the Tail) is east.

What is the brightest star in Serpens?

Unukalhai (Alpha Serpentis) at magnitude 2.6, an orange giant 73 light-years away. Its name means "the neck of the serpent" in Arabic.

When is Serpens best visible?

From June through August, when Serpens and Ophiuchus are high in the southern sky during evening hours, reaching their highest around midnight in July.

What does Serpens represent in mythology?

Serpens represents the serpent held by Asclepius (Ophiuchus), symbolising healing and rebirth. The snake coiled around a staff remains the international symbol of medicine today.

What deep-sky objects are in Serpens?

M5 (globular cluster, mag 5.7, one of the finest in the north), Eagle Nebula M16 (Pillars of Creation, mag 6.4, needs filter), and Omega Nebula M17 (Swan Nebula, mag 6.0).

What is the difference between Serpens Caput and Serpens Cauda?

Serpens Caput (the Head) is the western half containing M5. Serpens Cauda (the Tail) is the eastern half containing the Eagle Nebula and Omega Nebula, lying in the Milky Way.