Glossary term: Capricornus

Description: Capricornus is the smallest constellation in the Zodiac. The stars that make up this constellation are in the part of the sky that intersects with the ecliptic (the plane defined by the Earth's path around the Sun). In fact, all the constellations that comprise the Zodiac intersect the ecliptic. From Earth, we can regularly find the planets, and also the Sun, in the constellation Capricornus. In the case of the Sun this occurs from late January to mid-February (at that time, of course, we cannot see the constellation's stars). Capricornus is one of the 88 modern constellations defined by the International Astronomical Union, but goes back much further – it was already one of the 48 constellations named by the 2nd century astronomer Claudius Ptolemy. The stars that make up the constellation Capricornus are relatively faint. With a telescope, you can find the globular cluster M30 in Capricornus.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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A starry sky, including the diffuse glow of the Milky Way behind a stepped mud brick pyramid.

Galaxy Arm

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken from the south of Iraq in January 2022, this image shows a clear sky over one of the many ancient monuments in the region which looks like a Babylonian ziggurat. The Sumerians had invented these mountain-like buildings even before the invention of script; the earliest ziggurats appear around 4000 years before the common era. They look like the frustum of a pyramid and in Babylonian times often had temples on top. Next to the stairs of the ziggurat are the constellations of the southernmost part of the Zodiac, also invented in Babylon. Today, we call them Capricorn (left, with a planet in it) and Sagittarius, whose brightest stars form the asterism of the Teapot. For the Babylonians, Sagittarius was the god Pabilsang, the city god of Larak and a god of agriculture and war. He was also the husband of the mighty goddess of medicine, Gula, and his iconography is a hybrid creature holding a bow and arrow: a male human torso and head attached to the body of a horse with four legs, two gigantic wings and two tails — a horse tail and a scorpion tail. Such a creature did not exist in Greek mythology, so the Greeks reduced it to something they knew, a centaur holding a bow and arrow. This picture still did not make sense in Greek culture because centaurs were considered wild and cruel, and not intelligent enough to use a bow and arrow. Therefore, there was another Greek figure that existed simultaneously: a man with hooves instead of feet at the ends of his legs, a satyr, but this figure vanished in Roman times.  Capricornus is one of the most stable foreign creatures in the Zodiac and has been unchanged over millennia. It is depicted as a hybrid creature with the front part of a goat and the back part of a fish. This so-called Goat-Fish constellation has been recognised since the earliest writings of astronomy in Babylon. In Babylonian religion it is a good-natured, benevolent demon that protects humans, supports all healing processes and accompanies the god of wisdom and witchcraft. The Greeks simply adopted it and invented a saga for it. In Roman times, it became tremendously famous because emperor Augustus of Rome used it as his personal symbol, also imprinting it on coins and other political propaganda tools. In Sagittarius, there is also the bright bulge of the Milky Way. That this is hardly visible in this photograph is a result of modern civilization; the huge number of artificial lights that we use on Earth also illuminates the night sky and makes it impossible to see the Milky Way in areas where humans live.
Credit: Ruqayah Mohammed/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

The Milky Way appears as two vertical diffuse bands of light either side of a dark line, over a rocky outcrop.

The Pillar of Creation

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image shows the night sky over Tre Cime di Lavaredo, (Dolomites Natural Park), in the region of Veneto, Italy, in October 2021. The bright spot on the left-hand side is the planet Jupiter, appearing in the constellation Capricorn. To the right of Jupiter and below the two horn stars of Capricorn is the planet Saturn. Just above Jupiter we can see parts of Aquarius, one of the largest constellations and also part of the Zodiac. North of these constellations, left of the Milky Way, there are mostly faint stars. The brighter whitish one in the top left corner is Enif, a binary star in the constellation Pegasus. The Milky Way seems to emerge from a rock like celestial vapour. Roughly centred in the image are two bright stars left and right of the Milky Way: Altair and Vega, respectively. They seem to be separated by the galactic stream, as told in a popular Chinese folk story where they represent a loving couple. Today, in popular astronomy, the fairly bright star at the upper edge of the photograph is added to form a huge triangle with them, the Summer Triangle in the northern hemisphere. Altair is the brightest star of the Babylonian constellation Aquila, the Eagle. In ancient Babylon, it was said that the Eagle was carrying king Etana up in the air so that he could see Earth from above. Next to the Babylonian Eagle was the constellation of the Corpse, that returned only in Roman times when Ptolemy put it below the Eagle as the new sub-constellation “Antinous”. It is seen as the corpse (or soul) of the Roman emperor Hadrian’s favourite who had just died in the Nile. Vega is the bright white star to the right of the Milky Way. It forms part of the small constellation Lyra, famous for hosting the Ring Nebula, which is an impressive planetary nebula — a dying star blowing its gas into space. At the right edge of the image, three stars in a bent row appear rather prominently. This is the handle of the Big Dipper pointing downwards to a bright star close to the horizon: Arcturus, the bright star of the constellation Bootes (Greek: the Ploughman). This kite-like constellation is probably a pagan interpretation of the Babylonian god “Enlil” whose constellation also occupied that place in the sky. The Romans re-interpreted this figure as The Ox-Driver who controlled the Seven Oxen seen in the bright stars of Ursa Major. Directly right of Vega, there is the huge constellation Hercules and below it, directly to the left of Bootes, we find a half-circle of stars comprising the small constellation Corona Borealis, associated with Ariadne, daughter of King Minos of Crete in Greek culture. The lights seen in the bottom left side of the image are due to the reflection of artificial lights in the clouds.
Credit: Giorgia Hofer/IAU OAE

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons