All About The Capricornus Constellation

Capricornus is perhaps best known for its associated Zodiac sign, Capricorn—but the constellation has far more aspects to offer than only a horoscope reading.

Nearly every part of western civilization recognizes Capricorn, and perhaps even more know its general association with the visage of a goat. While this fame can lead to confusion regarding the actual name of the constellation, it is perhaps better this way.

Though Capricornus has a rich history and mythology, as well as several interesting objects comprising it—it is an incredibly dim constellation with a simple shape and relatively small size. Without the fame generated by the zodiac, it is possible the constellation would have faded into obscurity in our modern world. Luckily, this is not the case, and Capricornus continues to exist as one of the modern eighty-eight official constellations, worthy of its place now perineal in the night sky.

The Long History of Capricornus Constellation

Capricornus is another example of an ancient constellation that has been with humanity seemingly since our earliest days. In the Babylonian period, dating back as far as 2100 BCE, there is evidence that the constellation had already taken on some of its modern associations. Back then, during a period known as the Middle Bronze Age, it was referred to as MULSUḪUR.MAŠ, the goat-fish of Ea.

Ea was originally a Sumerian god known by the name Enki, and represented the ideas of water, knowledge, mischief, crafts, and creation. Ea later became Enki in the Babylonian and Assyrian traditions, and it is through surviving Babylonian seals (carved cylinders made from precious stone that could be rolled over clay tablets to replicate their design) that Enki’s associated goat-fish symbol comes down to us.

In the Greek tradition, Capricornus would continue to be associated with water and a goat-fish creature. It is another one of the forty-eight constellations listed in the 2nd century by Greek-Egyptian astronomer Ptolemy. By this time, the constellation had taken on its Latin name of Capricornus, translating roughly to “horned goat” or “goat horn.” While the imagery and water association had survived to this period, the surrounding myth had evolved into something widely-regarded and distinctly Greek.

The Greeks had several associated myths for Capricornus as well. In one story, the constellation represented Amalthea, the she-goat or goat-nymph who cared for the god Zeus in his infancy. In Greek mythology, Zeus was originally fated to be consumed by his father, the titan Cronos, who feared one of his children would be his downfall. Fearing the eventual fate of her son, Rhea, Zeus’ mother, hid him away in the care of Amalthea—or, the ‘tender goddess.’ It was under her care that Zeus was able to grow into the powerful god we typically imagine him as today.

Out of gratitude, Zeus placed Amalthea’s image in the sky as the constellation Capricornus. Additionally, he took one of her horns and endowed it with the ability to be ever-replenishing with food and drink. It is from this tale modern English adopts the term cornucopia, most often represented as a horn-shaped wicker basket filled with an assortment of fruits and vegetables.

Beyond that, Capricornus is sometimes identified as Pan, the god of the wild and shepherds—most famously depicted as half-man and half-goat. One story recounts how Pan gave himself a fishtail to dive into a river and escape Typhon—the same monster who pursued Aphrodite and Eros, who also turned themselves into fish to escape, and is represented by the constellation Pisces.

By Till Credner - Own work: AlltheSky.com

The Stars of Capricornus

While Capricornus may be a dim constellation with low-magnitude stars, they still carry with them their own distinctions. The brightest star is called Deneb Algedi, a name derived from the Arabic phrase ðanab al-jady meaning ‘the tail of the goat.’

This star is actually a system of three stars, with the central star classified as an A7m III white-giant star. This central star is double the mass of the sun and nearly double the radius. Its surface temperature is 7,301 kelvin (compared to the Sun’s 5,778 kelvin) and shines at 8.5 solar luminosities. Additionally, as an eclipsing binary system, the apparent brightness of the star as viewed from earth decreases when the dimmer star eclipses the central one, and increases when the primary star is at the forefront.

Dabih is the second brightest star of Capricornus, and comes from the Arabic word al-dhābiḥ, ‘the butcher.’ Dabih is actually a system of five stars, two of which can be viewed individually through binoculars. Known as Dabih Major and Dabih Minor, these stars are separated by .34 light years, and take nearly 700,000 years to orbit each other due to their immense distance.

The other interesting star of the constellation is Algedi, coming from the Arabic word al-jadii meaning, ‘the billy goat’ or ‘kid.’ This star is actually two different and unrelated binary-systems, and can be distinguished relatively easily with the naked eye.

Deep-Sky Pilgrim

Capricornus may be a small constellation in the night sky but the depth of space means it contains several interesting deep-sky objects. One of the most notable among them is Messier 30, a stellar globular cluster. As a mass of loosely associated stars, Messier 30 is roughly 12.9 million years old, and is currently in a retrograde orbit through our galaxy.

Given that it is moving against the general flow of our galaxy, this seems to suggest it was acquired from a passing satellite galaxy, rather than formed in the Milky Way. The cluster is also going through a process known as core collapse, meaning a great deal of stars are gravitating towards its center, forming one of the densest regions in the Milky Way.

How to Find and View

Capricornus is located in the southern hemisphere, amongst a group of constellations known as ‘the Sea’ or ‘the Water’ due to the general themes of their mythic histories. Nearby are Aquila, Sagittarius, Pisces Austrinus, and Aquarius. That said, Capricornus is best viewed in September and October where, in the Northern hemisphere, a line can be drawn from the star Vega and through Altair until it passes through Capricornus.

Visible too from the southern hemisphere, it can be seen at latitudes between +60 and -90. While not the brightest constellation in the night sky, Capricornus’ striking visualization as a goat-fish hybrid and complex mythology inspires plenty of wonder for any star gazer's imagination.