The constellation Serpens


Nome latino
Ambos os Hemisférios
June - August
637 deg²
Estrela mais brilhante
Unukalhai (HIP number 77070)
Open star cluster, globular clusters, gas nebula, ring galaxy
The constellation Serpens

The constellation Serpens is an extraordinary constellation located along the celestial equator. It is one of the 48 constellations described by the Greek-Roman astronomer Claudius Ptolemy in ancient times and represents a snake in Greek mythology. There are several interesting deep-sky objects located within its area.

Hemisphere, visibility, and area

The Serpens constellation is visible in both hemispheres, showing up in all regions between latitudes 74° N and 65° S. In the northern hemisphere, it is visible even above the Arctic Circle, and in the southern hemisphere, it can be seen almost up to the southern polar circle, with the exception of Antarctica.

The best months to observe the constellation in the night sky are from May to August. Serpens covers an area of around 637 square degrees, making it the 23rd largest constellation. What makes it special is that it is the only constellation whose area consists of two unconnected sky areas.

It is made up of two long chains of stars separated by the constellation Ophiuchus. It is divided into the areas of Serpens Caput (Head) and Serpens Cauda (Tail). The head is always visualized as a striking triangle on star maps.

The brightest star in both areas is named Unukalhai (Latin: α Serpentis, Alpha Serpentis) or simply Unuk, which comes from the Arabic word for "the snake's neck." It is a triple star system about 70 light-years away, with an apparent magnitude of roughly 2.6.

As Serpens is divided into two sky areas, it has many neighbors. The Serpent's Head is adjacent to the two astrological constellations of Virgo and Libra. The Corona Borealis, the Boötes, and Hercules are also in close proximity.

The Serpent's Tail is adjacent to the constellations of the Scutum and the Aquila. The astrological constellation Sagittarius is also nearby.

Ophiuchus, which separates the two areas, is adjacent to both the Serpent's Head and the Serpent's Tail.

Specialties in the constellation

The Milky Way passes through the Serpens, providing some exciting objects such as open clusters, globular clusters, a gas nebula, and a ring galaxy.

The gas nebula, also known as the Eagle Nebula, is designated as M16 (Messier 16) and NGC 6611. It has an apparent magnitude of around 6 and is estimated to be 7,000 light-years away. The Hubble Space Telescope captured impressive images of the massive dust and gas clouds in the nebula. Observing this object requires a medium-sized telescope.

Gas nebula M16, NGC 6611, Eagle Nebula
Gas nebula M16, NGC 6611, Eagle Nebula

The ring galaxy PGC 54559, also known as Hoag's Object, is another remarkable sight. It is an unusual ring galaxy with a nearly perfect circle of young blue stars around an older yellow core. Its distance is estimated to be approximately 540 million light-years, and it was discovered by American astronomer Arthur Hoag in the mid-20th century.


According to ancient mythology, the constellation represents the serpent that helped the physician Asclepius bring the dead to life. Asclepius observed how the snakes revived each other with herbs and applied this knowledge to the suffocated son of King Minos.

However, this displeased Hades, the god of the underworld, who asked his brother Zeus to end Asclepius' life. Zeus granted Hades' wish and had the physician killed by an arrow from a barbaric centaur.

To appease Asclepius' father, Apollo, Zeus placed Asclepius as a serpent bearer (Latin: Ophiuchus) along with the serpent in the sky.

Even today, the symbol of medicine is represented by the Rod of Asclepius, around which a serpent winds.

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