Glossary term: Saturn

Description: Saturn is the sixth planet from the Sun, and the second largest of the planets in terms of size and mass. It is a gas giant with a diameter of 120,000 kilometers (km), 9.4 times the radius of the Earth. Saturn has the lowest density of the Solar System planets, less dense than water on Earth. It has a mass of 95 times the mass of the Earth.

Its typical distance from the Sun is 1.4 billion km, about 9.5 astronomical units (Earth–Sun distances). Saturn takes 29.4 years to complete one orbit of the Sun. Astronomers have detected more than 140 moons or natural satellites orbiting Saturn. Among these moons, Titan is the largest, and is the only moon in the Solar System with a significant atmosphere.

Named after the Roman god of agriculture, Saturn is known as the jewel of the Solar System. It can be seen with the naked eye as a matte point of light in the sky. Even though it is over a billion kilometers away from Earth, the beautiful rings that surround it can be seen with a small telescope.

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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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The planet Saturn with pale brownish cloud ribbons and its thin and extended greyish rings


Caption: The NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 observed Saturn on 20 June 2019 as the planet made its closest approach to Earth this year, at approximately 1.36 billion kilometres away. The image shows coloured bands of gas on the planet's surface as well as its prominent rings made of ice and rocky material.
Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley) credit link

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The Milky Way rises from the horizon over a landscape with trees, water and the distant glow of city lights

Flowing Night Sky

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Time lapses of celestial patterns.   This time-lapse was shot from Slovakia in August 2020. By fixing the relative movement of the sky to Earth's rotation in some of the frames, we can experience a different perspective as a viewer. The Milky Way, our home galaxy, is visible throughout the whole video. The bright objects near the Milky Way are Jupiter and Saturn, close together, Jupiter being the brighter one. This video also shows the interaction of amateur astronomers observing the Perseids meteor shower with their telescopes pointed towards the sky. An unfortunate aspect of the art of astronomical observing, clouds can suddenly cover the whole sky. The fog occurs mostly because of the higher humidity after the rain. Most of the light trails in the sky are made by satellites, but some of them, appearing just very briefly and not very noticeably, are meteors, as the video was shot around the peak of Perseids meteor shower.
Credit: Robert Barsa/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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An all-sky image showing the Milky Way as a diffuse river of light, broken only by a mottled central band of dark patches

The Milky Way Across the Zenith

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This all-sky image shows our home galaxy, the Milky Way, crossing the zenith, the point just above the observer as seen from Nagano, Japan, in May 2019. Such images of the whole sky can be taken either with a fish-eye lens or with a convex mirror on the ground, the latter of which would show the photographer as well. Some of the brightest stars in the night sky can be seen in this image, as well as two of the giant planets of our Solar System: Jupiter, the brightest point in the bottom of this image, and Saturn, another bright point just to the opposite side of the Galaxy, to the bottom and next to the horizon. Directly right of the Milky Way and below Jupiter, we can spot the bright red star Antares, the primary star of the Japanese asterism of The Heart. Japanese constellations derive from ancient Chinese constellations, which were adopted with only slight or no changes. In this tradition, The Heart is the heart of the “Azure Dragon”, a super-constellation that represents the spring. In the Babylonian and Greco-Roman traditions, this area is considered the heart of the Scorpion. In Babylonian religion, the star is associated with Lisi, the child of the mother goddess, but in Greek mythology it is related to the planet Mars, because of its colour. The reddish colour also led to the star’s Chinese name “The Fire Star”. We know that this colour is caused by its relatively cool temperature. Going from Antares to the right of the image, we find the more northern parts of the sky. The bright star in the lower-right of the image, close to the horizon, is Arcturus, located in the modern constellation Boötes. While Antares and its surrounding area are considered the heart of the Azure Dragon, Arcturus and Spica (below the horizon) are two single-star asterisms forming its huge horn. Pointing towards it from above, at the right-hand edge of the image’s horizon, we can see the handle of the Big Dipper, or Plough, which is part of the constellation Ursa Major. The bright point to the right of the galaxy and just above the middle of the image is Vega, located in the modern constellation Lyra. Extending a line to the other side of the Galaxy and a bit lower in the image we can find Altair, in the constellation Aquila. From that point we extend another line to Deneb, the brightest star in the constellation of the Swan, also a bit higher in this image and completely flooded by the Milky Way. These three bright stars comprise the asterism known as the Summer Triangle in the northern hemisphere.
Credit: Ohnishi Kouji/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 bright Moon illuminates a beach. Three bright planets form a line below and to the right of the Moon.

To guard the Stars and the Sea Together

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns. This image composition is amazing. In the far background of the landscape we see a chain of mountains that seems to mirror the structure of the Milky Way in the sky above. The strong daylight-like colours of the landscape are caused by the Moon, the bright light at the top of the image. Taken in Kinabalu, Malaysia, in February 2019, this image shows the alignment of planets and the Moon, conveying the idea of the ecliptic as the central line of the Zodiac, the plane within which all planets orbit the Sun. The ecliptic is the central line of the Zodiac, so the region of about five to 10 degrees either side of the ecliptic is where the constellations of the Zodiac are located. Starting from the horizon towards the bottom left of the image we can see the planets Venus, Saturn and Jupiter. The planets have different cultural significance for people around the world, and are deeply embedded in social, religious and practical aspects of life. For example, Wardaman traditions of Indigenous Australians associate the planets with ancestor spirits who traverse the Celestial Road (ecliptic). The appearance and disappearance of planets in the sky are associated with various ceremonies. For example, when Venus starts being the “Morning star” after having been the “Evening star”, this marks the Banumbirr ceremony for the Yolnu people of Arnhem Land, in Australia. The image also shows the constellations Scorpius, Aquila, Lupus and Triangulum Australe, the asterism of the Teapot, and the two pointer stars Alpha and Beta Centauri. The constellations, asterisms and individual stars within them have significance in many different cultures. Malaysia, being close to the equator, has had connections to the north as well as to the south and almost the whole sky is visible over the course of the year. The star Antares is seen by the Kokatha people of the Western Desert as Kogolongo, the red tailed black cockatoo, while the Boorong refer to it as Djuit, the red-rumped parrot. The two stars which form the stinger of Scorpius (Shaula and Lesath), are called Karik Karik, the Australian Kestrel.
Credit: Likai Lin/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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