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Glossary term: Dust

Also known as dust grains or cosmic dust

Description: Unlike on Earth, dust grains in deep space are very tiny, with most being smaller than a thousandth of a millimeter. They represent an important constituent of the medium between stars called the interstellar medium. They are formed in different environments such as the outer layers of certain cool giant stars or supernovae and are dispersed into space when these stars begin losing mass. They are mostly composed of silicates, carbon compounds, and trace amounts of other elements. These could be coated with ices in cold, dense regions of the interstellar medium. They are mostly responsible for the interstellar extinction of starlight reaching us.

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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 smooth, diffuse glow extends from the horizon towards the upper left. In the top left there is a pair of two bright stars

Zodiacal Light over GTC Observatory

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken from La Palma, Canary Islands, in May 2022, this image captures the Zodiacal light, three prominent constellations (Gemini, Cancer and Auriga), and the Beehive Cluster, which appears as a small nebulosity to the unaided eye under dark skies. The Zodiacal light is a triangular white glow stretching along the ecliptic that is visible here at the western horizon shortly after sunset.The Canary Islands were considered the westernmost land of the inhabited world by the ancient Greeks. The dim shimmer in the Zodiac might have inspired the Greek philosopher Plato to think that the Sun leaves a trace of sunny glitter in its wake, and that the current path of the Sun, the ecliptic, has not always been its path. Plato believed that the Milky Way was a former path of the Sun and that its bright clouds are sparks of the Sun’s glory left behind. Today, we know that these two phenomena in the sky have different causes; while the Zodiacal light is really caused by reflection of sunlight from very tiny dust particles in the plane of the ecliptic, the Milky Way consists of billions of stars. The Zodiacal light is a smooth cone of light from the horizon upwards, while the Milky Way crosses the whole sky and also includes dark clouds. The Zodiac is described by Indigenous Australians as the Dreaming Road, and the Zodiacal light is a celestial rope connecting Venus to the Sun. The two bright stars in the top-left of the image are Castor (the bluish star) and Pollux (the whitish star), which are part of the constellation Gemini, the Twins. The two bright stars towards the bottom-right of the image are Menkalinan (the dimmer one) and Capella (the brighter one), which are part of the constellation Auriga, the Charioteer. The Wergaia people of Western Victoria in Australia see Castor and Pollux as brothers who hunt the kangaroo Purra in their stories. This has coincidental similarities to the Babylonian story, where they are considered two strong gods of the Netherworld, depicted with weapons. The Greco-Roman myth of the twins describes them as two brothers who accompanied the first ocean sailor, Jason, on voyages with the The Ship, Argo. A similar myth exists in the Blackfoot traditions of the First Nations people of Canada and the USA, where they are considered the two brothers Ashes Chief and Struck-behind.
Credit: Amirreza Kamkar/IAU OAE

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The Milky Way arches over an African grassland. Its diffuse glow is interrupted by a stream of dark patches.

Milky Way Arch over Amboseli National Park

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image was taken in July 2016 from the Amboseli National Park in Kenya, located close to the equator. In Egyptian mythology from northern Africa, the Milky Way was associated with a river sailed by gods and souls. The Zulu in South Africa interpret this pattern of dark and bright clouds of stars as an animal with black and white skin, whereas the South African Khoikhoi and San considered it “The Star’s Road”. In several South African cultures, the arch of the Milky Way is a pathway to the heavens formed by a mother goddess, according to a South African creation myth that was adopted in the 19th century from early ethnological research, but has vanished today. In the middle-right of the image we find the bright red star Antares in the modern constellation of the Scorpion and at the upper-left edge is the white star Vega that is considered a Male Steenbok by the peoples around Cape Town. Indigenous Australians have many names for the Milky Way. The Yolnu people of Arnhem Land in Australia’s Northern Territory refer to the Milky Way as Milnguya, the sky river. One of the prominent patterns in this image is associated with the contrast between the light and dark regions of the Milky Way. These dark regions are cool dense clouds of interstellar dust and gas, which block the light from stars behind them. One of the prominent patterns is that of the Celestial Emu referred to as Tchingal by several Indigenous peoples of south Australia. The head and beak of the emu (the Coalsack Nebula) lie to the bottom-left of the Southern Cross (seen in the far bottom-right of the image), and the body and legs stretch leftward from it. Other indigenous groups associate the dark regions with caves or waterways. The orientation of the emu over the year provides important clues as to when it is time to pick emu eggs, and when the eggs are hatching. In some months, when these clouds of the Milky Way are close to the horizon, they are not considered as emu at all but as two creeping crocodiles. The modern figure of the dark Pipe Nebula is clearly visible above the centre of the Galaxy; the smoke of this pipe reaches the colourful rho Ophiuchi region next to Antares in Scorpius, the orange-red star just above the Milky Way. Antares is referred to by the Boorong people as Djuit, the red-rumped parrot, while the Kokatha people of the Western Desert refer to Antares as Kogolongo, the red-tailed black cockatoo. In addition, some notable constellations can be seen: Cygnus, Aquila, Lyra, Scorpius, Sagittarius, Crux, and Centaurus. The pointer stars, Alpha and Beta Centauri, are occasionally interpreted as The Eyes of the Beast in some South African traditions.
Credit: Amirreza Kamkar/IAU OAE

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Over trees with thick trunks, the Milky Way, with several bright objects left and right, is bisected by a wide dark line.

Milky Way over Avenue of Baobabs

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image, taken from the Avenue of Baobabs, Morondava, Madagascar, in July 2017, shows the majestic band of the Milky Way, our home galaxy, together with a rich collection of constellations and asterisms: Crux, Centaurus, Scorpius, Sagittarius and the Teapot asterism. Towards the bottom left of the image we can see the Southern Cross and the pointer stars Alpha (the brighter of the two) and Beta Centauri, which help to distinguish it from similar-looking configurations. Some cultures in Africa associate the Southern Cross with a giraffe, while others associate the constellations with a pride of lions or even with the Tree of Life. Antares, the brightest star in the constellation Scorpius, is the orange-red star straight up from the middle baobab tree. To the Pokomo people from southwestern Kenya, Africa, the Milky Way is associated with the smoke emanating from a campfire lit by ancient people. The various people in South Africa, in contrast, have different star tales; the Khoikhoi from the region around Cape Town explained the colours of the red and white stars as red and white roots that were roasted on a fire and thrown towards the sky together with the ashes of the fire. The Xhosa from further east consider the Milky Way the raised bristle of a huge angry dog, while the Zulu from near Johannesburg interpret it as a stream of spears of their strongest warriors. Polynesian people, who were adept seafarers and navigators, see the constellation Scorpius as a fish hook, and refer to it as the demigod Maui’s Fish Hook. For the Djab Wurrung and the Jardwadjali people, the Southern Cross is part of a Dreamtime Story involving Tchingal, the Bram-bram-bult brothers (the pointer stars), their mother Druk (Delta Crux), and Bunya, the hunter who gets changed into a possum (Gacrux, red star at the top of the Southern Cross). In this image, the planets Saturn (the bright point above Antares) and Jupiter (the bright point at the bottom-right of the image close to the trunk of the baobab tree) are visible. Indigenous cultures have various stories associated with the planets, for example Kamilaroi and Wailan people associate Saturn with wunygal, a small bird. The Boorong people of Western Victoria associate Jupiter with Ginabongbearp, the chief of the old spirits (Nurrumbunguttias), who takes the totemic form of the sulphur-crested white cockatoo.
Credit: Amirreza Kamkar/IAU OAE

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The Milky Way looms over a bridge on a steep coastline. To the upper right is the bright, deep red star Antares

Drive

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image shows the Milky Way crossing the sky above the historical Bixby Bridge in Big Sur, a mountainous region in California, USA, in May 2021. The star directly above the shore is Antares, a red supergiant in the heart of the Scorpion. To its left, the clouds of the Milky Way seem to emerge from the same point of the horizon as the rocky landmass. Above the land, below the Milky Way in the left quarter of the image, is another bright star, Altair, the bright star in Aquila, the Eagle. The scorpion is considered a dangerous animal, so scorpion-men (human-scorpion hybrids) guarded the gate to the Netherworld in ancient Babylonian stories, as reported in the Gilgamesh saga. The Eagle, in contrast, appears in the Babylonian saga of King Etana who was taken to the sky by an Eagle and describes the world that he sees below him with increasing distance. Both heroes, Gilgamesh and Etana, are searching for the “herb of life” but one of them by going down, the other by travelling upwards. Gilgamesh aims to get back his dead friend Enkidu and to become immortal himself, while Etana is seeking the herb to help his wife become pregnant. The scorpion and the eagle are the animals supporting these heroes in their search, that ultimately remained unsuccessful. Gilgamesh finally learned that humans can only become immortal by their good deeds for humanity. The Eagle was also recognised in Greek culture, but it was only in Roman times that it became a messenger of a dead soul, carrying it towards the eternal stars. This was when Ptolemy created a constellation to represent the soul of Antinuous below the classical Eagle. This young friend and consultant of the Roman emperor Hadrian drowned in the Nile only seven years before the completion of the Almagest, and the whole Roman empire observed a state of national mourning. The Milky Way is seen as a “pathway of souls” by many cultures, but in the Babylonian culture, this is not the case. Still, in Greco-Roman philosophy, the bright white parts of it between Antares and Altair, at the intersection of the Milky Way and the Zodiac do have a meaning: Plato, Macrobius and other philosophers refer to it as “the X in the sky”, and the second Celestial Gate was probably considered to be here (the first one being the gate formed by the Hyades and Pleiades). These celestial pathways and gates, depicted above a gigantic bridge in the landscape and a site where the realms of land and ocean meet, make for an incredibly charged photograph. Additionally, the dark clouds in the Milky Way directly above the land form one of the two large dark constellations of the crocodiles, as interpreted by some people in southern Australia.
Credit: Marcin Zajac/IAU OAE

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Several observatory domes on a mountain top with the arching Milky Way behind.

Teide Observatory

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken in May 2022 in Teide National Park in Tenerife, Spain, this image shows the arc of the Milky Way galaxy crossing the sky, accompanied by prominent constellations over the professional telescopes located on the mountains of that island. While the telescopes and the people working with them may  ignore the constellations, the photographer managed to catch the Milky Way in such a way that it almost matches the shape of the mountain. The bright star in the top-left side of the image is Vega, one of the brightest stars in the night sky and located in the small constellation Lyra. Being a white star, it is the standard star astrophysicists use to define the colour scale. As it is also a relatively close star, only about 25 light-years away, with a relatively simple name, it frequently appears in modern science fiction, for example in Carl Sagan’s famous novel “Contact”, which was filmed in 1997 with Jodie Foster starring as a radio astronomer. The bright star seen below the galaxy and on the left half of the image is Altair, also one of the brightest stars in the night sky and located in the constellation Aquila. Together with Deneb — a star in the constellation Cygnus (the Swan) that is not visible in this image — Altair and Vega form the Summer Triangle, a characteristic asterism of popular astronomy in the northern hemisphere, where these telescopes are located. On the right side of the image we can see the constellation Scorpius. This is easily identified by its brightest star, Antares, the reddish star in the Scorpion’s heart. Below it, the whole body and tail of the Scorpion can be found and above it the celestial Scorpion's head is represented by three bright bluish stars. Below the tail and above the horizon, the constellation of Ara, the Altar, is half-visible, but like all the stars of Sagittarius in the Milky Way and the much fainter ones in Hercules and Ophiuchus above it, these constellations are more difficult to pinpoint in this photograph full of stars. The head of Ophiuchus is the relatively bright star in the middle between Vega and Antares. In addition to the huge size of this constellation, it is also important because it is the thirteenth one of the Zodiac, and the Sun spends roughly three weeks in Ophiuchus, after only five days in Scorpius. Furthermore, Ophiuchus represents the model for the mythological best doctor in the world, called Asklepios in Greek mythology, and Aesculab in Latin. His constellation praises all people working in medical professions, including nurses, pharmacists and doctors.
Credit: Curd-Christian Tengeler/IAU OAE

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Behind a jagged, wooded landscape, the Milky Way appears as two yellowish brown streams of light broken by patchy dark areas

Oregon Coast

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns:.   This image features the Milky Way, our home galaxy, over Oregon, USA, as seen in July 2021. It is obviously a composite because the stars are not reflected in the water. Still, it is nicely composed to suggest a similarity between the stream of water on Earth and the (mirrored) stream of stars in the sky. The Milky Way clearly dominates the sky in this image. As a prominent feature in the sky, the Milky Way has been associated with the religions and mythologies of many cultures. The best-known association from Greek folklore “explains” it as a stream of divine milk from the mighty mother goddess Hera, whose husband god Zeus frequently misbehaved (as he did in this case, causing this accident). Greek mythology, on the other hand, considered it to be the path of the souls, while ancient Greek science suggested several scientific explanations, all of which turned out to be false. The Ojibwe in North America, who live to the east of Oregon where this photograph was taken, also consider the Milky Way a Path for Spirits and a River of Souls. Looking at the foreground of the picture, this belief is even more understandable; it looks as if the rivers of Earth and heaven merge at the horizon. The prominent feature in the middle of the image is the dark region called the Pipe Nebula in the Milky Way. The smoke of this pipe goes to the right and ends almost at a treetop, where we find the orange star Antares in the heart of the Scorpion. In the middle of the image, below the Pipe, there is a huge dark area in the Milky Way with two prominent red spots. These spots are hydrogen clouds called the Cat’s Paw and the Lagoon, but in this image they look like the red eyes of great Manitou, the Great Spirit of the Iroquois Native Americans. The constellation of Sagittarius in this area is not recognisable because the image of the Milky Way is highly processed in order to display these dark features that are invisible to the naked eye.
Credit: Marcin Zajac/IAU OAE

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The Milky Way over a cloudy landscape. A triangle of bright objects is visible on the left of the image.

Equatorial Milky Way

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns: Equatorial Milky Way   Taken in Bromo-Tengger-Semeru National Park, Java Island, Indonesia, in March 2016, this image captures regions of the southern Milky Way and, at its left edge, the two planets Mars and Saturn. Mars appears orange and is similar in colour to the star Antares, whose Greek name — anti Ares — references this. Saturn is a little bit fainter than Mars, but clearly visible among the stars of Ophiuchus, above the Pipe Nebula and forming an isosceles triangle with Mars and Antares. Mars is on the top and Saturn is vertically below. Visible to the naked eye, both planets have significance in many cultures around the world. In Roman mythology Mars is the god of war and fertility, and Saturn the god of sowing and agriculture. Its Greek equivalent, the god Kronos, is also considered the regent of completion. Indigenous Australians, including the Kamilaroi and Wailan people, associate Saturn with “wunygal”, a small bird. Mars is called Iherm-penh (something burnt in flames) by the Anmatyerre people of the Central Desert, while the Kokatha people of the Western Desert associate Mars and the star Anatres with the red-tailed black cockatoo (Kogolongo). In the middle of this photograph, the most famous southern constellations are clearly recognisable: the Southern Cross (Crux), the pointer stars, Alpha and Beta Centauri, the dark Coalsack Nebula and the red Eta Carina Nebula, which is not visible to the unaided eye but is prominent in modern photographs. In the 19th century, the star eta Carinae had been the second-brightest star in the sky for some time, but since it varies irregularly, it has hardly been recognisable in recent decades, and its future visibility is unpredictable. Triangulum Australe is visible between the pointer stars and the Scorpion, and in the constellation of Centaurus, the bright globular star cluster Omega Centauri is clearly displayed. It was considered a “nebulous star” since antiquity and, thus, was listed in star catalogues for at least 2000 years. Only within the last century did astronomers discover that globular star clusters are in the halo of our galaxy and that this one consists of roughly 10 million stars. The dark regions in the Milky Way, which are cool, dense clouds of dust and gas, form the head and body of the Celestial Emu Tchingal. Together with the Southern Cross and the pointer stars, they appear in the Dreamtime stories of many Indigenous Australians. One story associated with the Djab Wurrung and the Jardwadjali people is part of a Dreamtime Story involving Tchingal, the Bram-bram-bult brothers (the pointer stars), their mother Druk (Delta Crux), and Bunya the hunter, who gets transformed into a possum (Gacrux, the red star at the top of the Southern Cross).
Credit: Giorgia Hofer/IAU OAE

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The diffuse glow of the Milky Way broken by dark patches. Right, the red star Antares forms the top of a hook-like pattern

Milky Way Arch over La Palma

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image, which shows the majestic band of the Milky Way and a range of culturally significant patterns, was taken in May 2022 at a very high altitude from the Roque de los Muchachos Observatory in La Palma, from which one can see the clouds below. Some prominent star patterns include Scorpius, Sagittarius, Lyra, Cygnus, Aquila, the Summer Triangle asterism, and the Teapot asterism. As the Canary Islands used to be a starting point for European sailors to explore the world, we use this place to point to the many indigenous cultures they encountered. Most notably it is the dark patterns within the band of the Milky Way that hold significance for many Indigenous cultures around the world. The dark patterns are in fact dense, cool clouds of gas and dust that block the light from stars. Indigenous people see caves, waterways and various patterns associated with the dark regions of the Milky Way. The constellations and patterns hold different cultural significance and interpretations for different people. For example, the constellation Scorpius is referred to by Polynesian people as the demigod Maui’s Fishhook. The Yolnu people of Arnhem Land associate Scorpius with a crocodile called Ingalpir. Some Indigenous Australian groups associate stories with individual stars within Scorpius, most notably Antares, the orange-red star in the top right of the image above the band of the Milky Way. Next to the Scorpion and above the bright centre of the Milky Way, there is a prominent dark cloud that is called the Pipe Nebula by modern astrophotographers. The smoke of this pipe goes up to rho Ophiuchi. This and all the other dark clouds in the Milky Way together form the backbone of heaven for some tribes, and an animal with black-and-white skin for South African Zulu people. The nomenclature of bright stars also has cross-cultural roots. For example, Vega (the bright blue star towards the top of the image) comes from the Arabic waqi, from al-nasr al-waqi, the Eagle who throws himself down (in order to hunt). This contrasts with the Flying Eagle, Altair, also derived from Arabic. Antares is a Greek word meaning “the one similar to Mars”, referring to its colour. The star name Shaula in the stinger of the Scorpion is a modern version of the Babylonian or even Sumerian star name.
Credit: Amirreza Kamkar/IAU OAE

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The Milky Way arches over a mountain-top building. Its diffuse glow is broken by dark patches and is brighter on the right

The Moon and Milky Way arch Above the Golden Hall

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken in April 2021 from the top of the Laojun Mountain in China, this image shows a panoramic view of the Milky Way over the Golden Hall called “Yuhuangding” as a symbol of wealth. In China, the Milky Way is considered a huge stream like one of the big rivers. It separates the Cowherd (Altair) and his beloved Weaving Girl (Vega) and it has a Celestial Ford in the northern dark cloud in the modern constellation Cygnus. The Milky Way appears as a whitish arch as we cannot distinguish all the individual stars, but instead see the accumulation of light from them. It is a disc-shaped galaxy and the Solar System is located within one of its spiral arms, so we see it from inside, which gives it the shape of a band in our sky. It is associated with the religions and mythologies of several cultures. The modern term Milky Way derives from Greek folklore as the milk spread in the sky by the mother goddess Hera, when she unwillingly breastfed young Heracles. This son of Zeus and a mortal woman was put next to her while she was asleep but from his strong sucking she woke up and realised she was feeding an unknown child, and immediately pushed the child away. Greek philosophers like Plato considered the glittering band in the sky to be the traces of a former path of the Sun. Alternatively, for the Tupi-Guarani indigenous mythology from South America, the Milky Way represents the “path of tapir”. For some Australian native peoples, its dark clouds formed the shape of an emu if high in the sky, and of crocodiles if low on the horizon. For many southern African, South American and Australian cultures, it was considered a pathway to or from heaven. At the right edge of the image, we can recognise the modern constellation Scorpius with its most prominent star, Antares, the reddish star just above the Milky Way. The brightest point seen in the centre bottom of the image is the rising Moon with Jupiter next to it. A few constellations can be distinguished in this image, including Corona Australis, a faint arc-shaped constellation located to the bottom right. Just above the Southern Crown, we can see the Teapot asterism as part of the Sagittarius constellation. Since Sagittarius lies next to the centre of the Milky Way, many structures such as star-forming regions, globular clusters and planetary nebulae can be found within its boundaries. In Sagittarius, we also find a supermassive black hole four million times as massive as our Sun. At the left side of the band, we can identify the bright star Deneb in the constellation Cygnus, The Swan, through which the Milky Way runs, meaning that a variety of star clusters are found in this constellation.
Credit: Likai Lin/IAU OAE

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The curve of the Milky Way bisected on the left by a huge dark arch. Below appear two bright, diffuse patches.

The Milky Way Over Anglers Reach

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   The Milky Way and several astronomical objects are seen in this image taken from the southern hemisphere, in Anglers Reach, Australia, in April 2022. On the bottom-left side we can identify the constellation Scorpius with its brightest star, Antares, the reddish spot just above the arc. Some prominent but small southern constellations can also be seen: the dominating bright stars in the middle-left of the image in the Milky Way are the four bright stars of Crux (the Southern Cross) and to its left the two pointer stars, alpha and beta Centauri. Crux points towards the southern celestial pole, which is not marked by a bright star, and The pointer stars point towards Crux, distinguishing it from the asterism of the False Cross in the constellation Argo. Crux features on the national flags of Australia, Brazil, Papua New Guinea, Samoa and New Zealand. As Crux lies in the brightest parts of the Milky Way, the dark cloud of the famous Coalsack Nebula is prominent next to the bright stars. It forms one of the dark constellations in South American, South African and Australian indigenous cultures. The huge Australian dark constellation of the Emu is almost completely above the horizon in this image, stretching from its head in the Coal Sack to the horizon. In Greek antiquity, the stars of Crux also belonged to the constellation Centaurus, a hybrid creature with a human torso and head attached to a horse body with four legs. The Greek centaur represents Chiron, the wise teacher of all Greek heroes. Its brightest star is Rigil Kentaurus (Alpha Centauri), the front hoof of the centaur. Just below it, we find the small constellation Triangulum Australe. The triple star system of Alpha Centauri is our Sun’s nearest stellar neighbour. Along the Milky Way in the middle-right of the picture we find the huge constellation Argo, the Ship. The smaller ancient constellation Argo was extended by Dutch navigators around 1600, and the number of stars in this constellation was then so big that the 18th-century French mathematician Lacaille needed to introduce subtitles for Argo in his star catalogue. In doing so, he invented the constellations Puppis, Carina and Vela. In Carina, the Keel of the ship, this reddish photograph clearly displays the Carina Nebula. At the right edge of the image we can spot the brightest star in the night sky, Sirius, while the second brightest star, Canopus, the rudder of Argo, the Ship, dominates the area under the arch of the Milky Way. Also below the Milky Way arc, we can see the Large Magellanic Cloud and the Small Magellanic Cloud, which are small satellite galaxies of our own Galaxy.
Credit: Lucy Yunxi Hu/IAU OAE

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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

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