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, in astronomy

Saturn, in astronomy, 6th planet from the sun.

Astronomical and Physical Characteristics of Saturn

Saturn's orbit lies between those of Jupiter and Uranus; its mean distance from the sun is c.886 million mi (1.43 billion km), almost twice that of Jupiter, and its period of revolution is about 291-2 years. Saturn appears in the sky as a yellow, starlike object of the first magnitude. When viewed through a telescope, it is seen as a golden sphere, crossed by a series of lightly colored bands parallel to the equator.

Saturn, a gas giant like Jupiter, is covered with a thick atmosphere composed mainly of hydrogen and helium, with some methane and ammonia; its temperature is believed to be about −270℉ (−168℃), suggesting that the ammonia is in the form of ice crystals that constitute the clouds. Like Jupiter's interior, Saturn's consists of a rocky core, a liquid metallic hydrogen layer, and a molecular hydrogen layer. Traces of various ices have also been detected. The wind blows at high speeds—reaching velocities of 1,100 mph (1,770 kph)—across Saturn. The strongest winds are found near the equator and blow mostly in an easterly direction. At higher latitudes, the velocity decreases uniformly and the winds counterflow east and west. Because no permanent markings on the planet are visible, the planet's exact period of rotation has not been determined. However, the period of each atmospheric band varies from 10 hr 14 min at the equator to about 10 hr 38 min at higher latitudes. This rapid rotation causes the largest polar flattening among the planets (over 10%). Saturn is the second largest planet in the solar system; its equatorial diameter is c.75,000 mi (120,000 km), and its volume is more than 700 times the volume of the earth. Its mass is about 95 times that of the earth, making Saturn the only planet in the solar system with a density less than that of water. Saturn has been encountered by four space probe missions: Pioneer 11 (1979), Voyager 1 (1980), Voyager 2 (1981), and Cassini and Huygens (2004–17). Among the discoveries made by the Voyager probes was a magnetosphere (a region of charged particles consisting primarily of electrons, protons, and heavy ions captured partly from the atmosphere of the satellite Titan) that encloses 13 of Saturn's satellites and its ring system. Huygens landed on Saturn's moon Titan in 2005 and returned photographs of its surface.

The Ring System

Saturn's most remarkable feature is the system of thin, concentric rings lying in the plane of its equator. Although first observed by Galileo in 1610, it was not until 1656 that the rings were correctly interpreted by Christiaan Huygens, who did not reveal his findings about their phases and changes in shape until his treatise Systema Saturnium was published in 1659. Saturn's rings were believed to be unique until 1977, when very faint rings were found around Uranus; shortly thereafter faint rings were also detected around Jupiter and Neptune.

Although the main ring system is almost 167,770 mi (270,000 km) in diameter, it is only some 330 ft (100 m) thick. From earth, this system appears to consist mainly of two bright outer rings, denoted A and B (lettered from the outermost), separated by a dark rift—discovered by the Italian-French astronomer Gian Domenico Cassini—known as Cassini's division, plus a third, faint inner crepe ring (denoted C). The Encke Division, or Encke Gap, which splits the A ring, is named after the German astronomer Johann Franz Encke, who discovered it in 1837. In 1859 the Scottish physicist James Clerk Maxwell showed that the main rings must consist of countless tiny particles each orbiting the planet in accordance with the laws of gravitation. In the 1980s pictures from the Voyager probes showed four additional rings. The exceedingly faint D ring lies closest to the planet. The faint F Ring is a narrow feature just outside the A Ring. Beyond that are two far fainter rings named G and E. In 2009 an enormous but faint ring consisting of tiny dust particles was discovered extending from 3.7 to 7.4 million mi (6 to 12 million km) away from Saturn. Lying at a 27° angle to the main rings, this ring has a retrograde orbit and is believed to have originated in material ejected from the moon Phoebe by small impacts. When edgewise to the earth Saturn's main rings appear as a nearly imperceptible ribbon of light across the planet; this occurs twice during the 291-2-year period of revolution. Twice during each orbit the rings reach a maximum inclination to the line of sight, once when they are visible from above and once when visible from below.

The Voyager 1 (1980) and 2 (1981) space probes revealed incredible new detail as they passed within 78,000 mi (126,000 km) and 63,000 mi (101,000 km) of Saturn, respectively. They recorded hundreds of tiny rings that are grouped into the seven major rings. The three brightest rings (A, B, and C) dissolved into more than 1,000 narrow ringlets, 100 of which are in the Cassini division. The outer F ring was found to contain braids, knots, and strands, possibly caused by nearby moons that shepherd it, that is, limit the extent of a planetary ring through gravitational forces. The main rings are believed to have been formed mainly from larger satellites that were shattered by the impact of comets and meteoroids; geyserlike eruptions on Enceladus contribute material to the E ring. Cassini revealed that the rings consist mainly of water ice.

The Satellite System

Saturn has 82 confirmed natural satellites, many of which have not been named. Five of the discovered satellites have not been found since they were first identified (2004, 2007) and are considered lost. Because the increasing number of satellites makes it difficult to continue to name them after Greek Titans, as the first moons to be discovered were, a scheme was adopted for the outer satellites. These are now named after the giants of other cultures: Inuit, Norse, and Gallic. The satellites may be divided into nine groups for convenience. In the order of their distance from Saturn, the groups are shepherd (satellites whose orbit is within or just beyond Saturn's ring system), co-orbital (two satellites that share the same orbit and trade positions within it on a regular basis), inner large (large satellites within the E ring), Alkyonide (small satellites within the inner large group), Trojan (satellites that are co-orbital at Lagrangian points), outer large (large satellites beyond the E ring), and Inuit, Norse, and Gallic (each a group of outer satellites that have similar orbits). There are also ring moonlets orbiting in the B and A rings.

The five confirmed shepherd satellites are Pan, Daphnis, Atlas, Prometheus, and Pandora, are named. The co-orbital group comprises Epimetheus and Janus, but the shepherds Prometheus and Pandora also share an orbit. The inner large group comprises four satellites, Mimas, Enceladus, Tethys, and Dione; the three Alkyonides (Methone, Anthe, and Pallene) have orbits between Mimas and Enceladus. The Trojan group, also found within the inner large group, comprises four satellites, Telesto, Calypso, Helene, and Polydeuces. The outer large group comprises four satellites, Rhea, Titan, Hyperion, and Iapetus. The Inuit group comprises seven satellites, five of which are named: Kiviuq, Ijiraq, Paaliaq, Siarnaq, and Tarqeq. Of the 46 satellites comprising the Norse group, only 21 are named: Phoebe, Skathi, Skoll, Greip, Hyrrokkin, Jamsaxa, Mundilfari, Bergelmir, Narvi, Suttungr, Hati, Farbauti, Thrymr, Aegir, Bestia, Fenrir, Surtur, Kari, Ymir, Loge, and Fornjot. The Gallic group consists of four satellites, Albiorix, Bebhionn, Erriapus, and Tarvos; one additional satellite may be a member of this group.

Almost all of Saturn's inner moons form a regular system of satellites; that is, their orbits are nearly circular and lie in the equatorial plane of the planet; almost all of the outer moons' orbits are inclined. Except for Hyperion, which has a chaotic orbit, and Phoebe, all the satellites are believed to have synchronous orbits; that is, their orbital and rotational periods are the same, so that they always keep the same face turned toward Saturn. The largest satellite, Titan, is 3,200 mi (5,150 km) in diameter and has the size and cold temperatures necessary to retain an atmosphere; it is the only natural satellite in the solar system with a substantial atmosphere.

Saturn has six major icy satellites that can be easily seen through earth-based telescopes. The most prominent feature of heavily cratered Mimas, the innermost of the six, is a large impact crater about one third the diameter of the satellite. Certain broad regions of Enceladus are uncratered, indicating geological, mostly likely cryovolcanic, activity that has resurfaced the satellite within the last 100 million years. Tethys also has a very large impact crater, as well as an extensive series of valleys and troughs that stretches three quarters of the way around the satellite. Both Dione and Rhea have bright, heavily cratered leading hemispheres and darker trailing hemispheres with wispy streaks that are thought to be produced by deposits of ice inside surface troughs or cracks. Iapetus, the outermost of the large icy satellites, has a dark leading hemisphere and a bright trailing hemisphere.

The remaining satellites are smaller. The two largest of these, the dark-surfaced Phoebe and the irregularly shaped Hyperion, orbit far from the planet; the Norse group of satellites orbit with retrograde motion, i.e., opposite to that of the planet's rotation. The smallest satellites, less than c.6 mi (10 km) in diameter, include Daphnis, the Alkyonides, Polydeuces, some of the Inuit and Gallic groups, and nearly all of the Norse group.


, in Roman religion and mythology
Saturn, in Roman religion and mythology, god of harvests, later identified with the Greek Kronos. Little is known of the origins of his cult. His reign was regarded as the Golden Age. He was the husband of Ops and the father of Jupiter, Juno, Ceres, Pluto, and Neptune. It was said that after the fall of the Titans, Saturn fled to Italy, where he settled on the Capitoline Hill, civilized the people, and taught them the arts of agriculture. At his festival, the Saturnalia, held at first on Dec. 17 but later extended for several days thereafter, gifts were exchanged, schools and courts were closed, war was outlawed, and slaves and masters ate at the same table.
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(sat -ern) The sixth planet of the Solar System and, with an equatorial diameter of 120 537 km, the second largest. It orbits at a distance of between 9.01 and 10.04 AU from the Sun once every 29.46 years; oppositions recur two weeks later each year. It has a polar diameter of 107 519 km so that its oblateness, 0.108, is the highest of any planet. Its mean density, 0.7 times that of water, is lower than that of any other planet. Before 1978 Saturn was thought to have 10 satellites, the three largest being Titan, Rhea, and Iapetus; the number is currently 47. Orbital and physical characteristics of planet and satellites are given in Tables 1 and 2, backmatter.

Saturn is the outermost of the five planets that were known to the astronomers of antiquity. The telescopic appearance of the planet is dominated by a prominent and beautiful system of rings (see Saturn's rings) that lie in the plane of Saturn's equator, tilted by 27° with respect to its orbit. This tilting leads first one face of the rings, and then the other, to be inclined towards the Sun and the Earth by up to 27°. At approximately 15-year intervals, the rings become edge-on to the Earth and all but disappear. The bright rings, about 270 000 km across, can add appreciably to Saturn's average apparent magnitude of 0.7 at opposition, when the globe and rings are 19 and 44 arc seconds wide respectively.

Saturn's disk appears similar to that of Jupiter in being crossed by yellowish dark and light cloud bands running parallel to the equator; these are called belts and zones respectively. They are less prominent, however, than those of Jupiter and spots within them are much less common. The spots, typically white, that have been followed indicate that Saturn, like Jupiter, rotates more rapidly near the equator (in 10 hours 14 minutes or less) than at high latitudes (about 10 hours 40 minutes).

Saturn and its environment were studied by the Pioneer 11 probe in 1979, the Voyager probes in 1980 and 1981, and the Cassini/Huygens spacecraft from 2004. The Cassini craft was scheduled to make 74 orbits of the planet in the space of four years. These probes provided considerable information on the meteorology and atmosphere of Saturn, which resemble those of Jupiter. Like Jupiter, Saturn emits more radiation than it absorbs from the Sun and probably has an internal primordial energy reservoir. Escaping heat may drive the atmospheric convection processes that give rise to the observed cloud banks, probably of ammonia crystals at 100 K. The Saturnian weather systems, like those of Jupiter, are strongly zonal. At the equator the cloud top winds reach more than 500 m s–1. There is evidence of a wide range of cloud systems of varied morphologies: the white spots are anticyclonically rotating systems and have features identical with Jupiter's Great Red Spot; trains of vortex streets are seen in northern midlatitudes. Although there is a strong internal heat source, analyses of the Voyager data have shown that Saturn (and also Jupiter) and the Earth drive their meteorological systems in the same way, with energy being transported from the small-scale features into the main flow. Spectroscopic studies indicate hydrogen, methane, and ethane in the upper atmosphere; hydrogen probably forms the bulk of Saturn's mass.

Models for the internal structure of Saturn suggest an Earth-sized iron-rich rocky core with a 7500-km outer core of ammonia, methane, and water. This is enclosed by about 21 000 km of liquid metallic hydrogen above which lies liquid molecular hydrogen.

Saturn's magnetic field was detected by the Pioneer 11 probe. It has the same direction as Jupiter's field but is about 20 times weaker. Surprisingly, the magnetic axis corresponds almost exactly with Saturn's rotational axis. Pioneer also discovered radiation belts, mainly comprising energetic electrons and protons. Saturn emits intense radio waves that are thought to be generated as synchrotron emission from the electrons spiralling in the magnetic field. Saturn's rings and its inner satellites sweep away these charged particles. The interactions with the rings give rise to electrostatic discharges and assist in the formation of the spoke patterns in ring B. The Cassini/Huygens probe found also that Saturn's radio emissions are generated along with aurorae on the planet.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Enlarge picture
An illustration of Saturn in his chariot with his zodiacal signs Capricorn and Aquarius as wheels. From a mid-seventeenth-century edition of Johannes Indagines’s Introduciones Apotelesmatica. Reproduced by permission of Fortean Picture Library.


(religion, spiritualism, and occult)

Saturn is the last planet in the solar system that can be seen with the naked eye. Its system of rings makes it stand out as a spectacular sight when seen with a telescope. Saturn has the lowest density of any planet in the solar system and is made up of primarily of hydrogen and helium molecules. Its rings are formed of either matter that was torn apart by Saturn’s gravity or material that failed to accrete into a moon when moons were forming. The rings are inclined by 27° to the planet’s orbit. According to Jay M. Pasachoff’s Contemporary Astronomy, there are 9 moons that have long been known and several others have been detected in modern times. Saturn’s cycle around the Sun is 29.47 years and mirrors the 29-month lunar cycle. Saturn spends 4½ months a year in its retrograde phase. It annually travels an average of 22° forward and 7° retrograde in zodiacal longitude. Due to its distance from the Sun and Moon the ancients attributed Saturn with the primary qualities of cooling and drying.

In Greek mythology, Saturn was Kronos (Cronos), one of the Titans who were among the first children of Heaven (Ouranos) and Earth (Gaea). Ouranos hated some of the first offspring who were horrible monsters and he hid them in secret places within the earth. Gaia was angered at the treatment of her children and appealed to the Cyclopes and Titans for help. Kronos lay in wait for his father and castrated him with a sickle. From that time on for untold ages, Kronos became lord of the universe, according to Edith Hamilton’s Mythology. After being overthrown by his son Zeus, Kronos is said to have gone to Italy and ruled over the Great Golden Age. The Romans called him Saturnus, known as the god of agriculture and harvest who founded civilization and the social order. The great feast of Saturnalia is held annually in winter. It was thought that the Golden Age returns during the days the feast lasted. In Christian times, this holiday became Christmas and represents the birth of the Divine Child born at the Winter Solstice. At the turning of the year, old Father Time, who carries a sickle, is replaced by the New Year’s Eve baby.

The passive side of Saturn is solitary, austere, depressive, downcast, miserable, demanding, inactive, sedentary, and immobile. The active side of Saturn is disciplined, determined, driving, sustained, persistent, hard working, and undaunted. In the Hellenistic system, according to Edith Hamilton’s Mythology, the star of Kronos was assigned the special essence of ignorance and necessity. Saturn traditionally rules the masculine sign Aquarius that opposes the Sun, and the feminine sign Capricorn that opposes the Moon. It is exalted in Libra, in its fall in Aries, and in its debility in Cancer. When Saturn has essential dignity it operates more from the active qualities and can produce positive results. With little dignity its significations manifest in more malefic form. It rules the Air triplicity in a diurnal chart.

Saturn is a diurnal planet by sect. This means that Saturn in a daytime chart is more at his best. Joseph Crane explains Saturn’s sect differences in A Practical Guide to Traditional Astrology:

A diurnal Saturn is organized and disciplined, but also responds to novelty and change. He provides the virtues that one needs to flourish in the world—self-discipline, self-reliance, consistency, responsibility, and frugality … a nocturnal Saturn can become more melancholy, more prone to punishing oneself or others. Here gravity can become density and a greater sense of life’s futility. Indeed, diurnality balances some of these saturnine extremes!

Saturn is the most important of the planets in relation to terrestrial boundaries. Saturn is associated with agriculture, and the process and handwork of harvest. Things that take time to develop and endure over time are representative of Saturn’s nature. Therefore Saturn is linked to time, age, progress, productivity, maturity and wisdom. In the rank of social structure, Saturn is the administrator, taskmaster, tax collector, guardian, and teacher. It procures reputation and notable rank, according to Vettius Valens, Book I, Chapter I. Its orientation can be toward perfection that requires diligent and disciplined effort, or efforts that can be blocked and limited by restriction, doubt, and lack of skill. It brings what is deserved or earned. Honors, respect, and authority can be granted after efforts have been made. At its most malefic it judges, punishes, rejects, and brings accusation, tears, captivity, exposure of deceit, and orphanhood.

Classical diseases and health problems associated with Saturn are those proceeding from cold, obstructions, and decay, such as melancholy, agues, all nervous diseases, epilepsy, black jaundice, toothache, cold defluxions, catarrh, atrophy, fistula, leprosy, palsy, apoplexy, and dropsy, according to James Wilson’s Complete Dictionary of Astrology. Saturn’s ailments are chronic and many are associated with aging, such as arthritis, sclerosis, skin diseases, skeletal deformities, hardening of arteries, cancer, congestion, constipation, consumption, deafness, birth defects, falls and bone fractures, gout, growths, halitosis, paralysis, polio, retardation, rheumatism, rickets, starvation, stones in the body, tremors, tooth aches and extractions, weakness, and weight gain, according to Rex E. Bills’s The Rulership Book, A Directory of Astrological Correspondences.

In modern astrology’s psychological view, Saturn’s influence in personality lends a restricted bias toward the perception of how life should operate based on parental, social, and cultural standards. It relates to the kind of intelligence that is factual, correlating information into organized, systematically logical knowledge. It is traditional rather than original. Saturn gives strong leanings toward conformity and social acceptance, while resisting change and rejection.

Liz Greene, Jungian psychologist and author of Saturn: A New Look at an Old Devil, gives the modern view of Saturn:

Saturn symbolizes a psychic process as well as a quality or kind of experience. He is not merely a representative of pain, restriction, and discipline; he is also a symbol of the psychic process, natural to all human beings, by which an individual may utilize the experiences of pain, restriction, and discipline as a means for greater consciousness and fulfillment …. The psychic process which Saturn symbolises seems to have something to do with the realisation of this inner experience of psychic completeness within the individual.

Saturn in the natal chart by sign illustrates the lessons necessary for the individual to define himself and his focus in order to integrate into society. Saturn has a 2½-year passage through each sign. The element of the sign highlights the area of greatest restriction that needs to be restructured through the individual’s process of development.

Hellenistic astrology gave greater emphasis to planets ruling houses than planets in houses. Modern astrology has given more emphasis to planets in houses. The houses in the chart ruled by Saturn are the places where it has greatest influence on the native’s life experiences. Saturn rules the natural tenth and eleventh houses and has its joy in the twelfth house. Using traditional rulership of signs, Saturn rules both Capricorn and Aquarius. Modern astrologers have adopted Uranus as the ruler of Aquarius.

In Jyotish (Vedic astrology), Saturn is known as Shani, or Sanaiscara, which means, “moving slowly.” Saturn is the farthest visible planet from the Sun. One story tells of how Saturn was born of the Sun. The Sun’s wife grew tired of the glare and heat from her husband and decided to visit her family. She left her shadow in her place. The Sun could not tell the difference between his wife and her shadow and had sex with the shadow. Out of this union Saturn was born. When the ruse was discovered the Sun banished Saturn and refused to acknowledge him as his son. This is why Saturn is not a friend to the Sun.

The other important story about Saturn involves Ganesha, the elephant-headed god. After many centuries of practicing meditation and other forms of spiritual practice, Parvoti decided to have a child with her husband Shiva. Shiva stayed up in the mountains meditating while Parvoti went down the mountain and gave birth. The child was exceptional and like any proud mother, Parvoti called all the gods to come and see her beautiful son. All the gods came and cooed and murmured in amazement, except for Saturn who stood away staring at his feet. Parvoti took offense and demanded that Saturn look at the child. Saturn tried to explain that nothing good could come from his glance, but Parvoti insisted. Saturn raised his head and just barely looked at the child, and the child’s head was burnt up into ash. Everyone was aghast and very upset, most especially Parvoti. To soothe her Brahma went to find a new head for the child. The first creature he found was a huge bull elephant. He took the elephant’s head and fixed it on the body of the child. That is how Ganesha got his head. (There is another version where it is Shiva who cuts off the child’s head because he did not know Parvoti had gone off to have a child.)

In the celestial cabinet, Saturn is the servant. He represents the outcasts of society, beggars, and people who do not follow religious practices. His elemental quality is air, and his gender is neutral. He is the indicator for disease, death, and all sorts of bad things. Ironically, a well-placed Saturn indicates good longevity.


Bills, Rex E. The Rulership Book, A Directory of Astrological Correspondences. Richmond, VA: Macoy Publishing & Masonic Supply Co., 1971.
Crane, Joseph. A Practical Guide to Traditional Astrology. Orleans, MA: Archive for the Retrieval of Historical Astrological Texts, 1997.
Greene, Liz. Saturn: A New Look at an Old Devil. New York: Samuel Weiser, 1976.
Hamilton, Edith. Mythology. Boston: Little, Brown, 1942.
Masco, Maire. Jyotish Saturn ideas from correspondence by email.
Pasachoff, Jay M. Contemporary Astronomy. 3d ed. Philadelphia: Saunders College Publishing, 1985.
Schmidt, Robert, translator. Vettius Valens, Book I, Chapter I. Cumberland, MD: Phaser Foundation, 2002.
Wilson, James. A Complete Dictionary of Astrology. Islington Green, London, England: William Hueges, 1819.

—Norma Jean Ream

The Astrology Book, Second Edition © 2003 Visible Ink Press®. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



in ancient Roman religion and mythology, the god of seed sowing. He was identified with the ancient Greek god Cronus. Annual festivals were held in Saturn’s honor.



the sixth major planet from the sun in the solar system; its astronomical symbol is b. Saturn is one of the giant planets. The semimajor axis of its orbit, that is, the mean distance from the sun, is 9.54 astronomical units, or 1.43 billion km. The eccentricity of its orbit is 0.056, the largest among the giant planets. The orbit is inclined 2°29’ to the plane of the ecliptic. Saturn completes one revolution around the sun (sidereal period of revolution) in 29.458 years at an average velocity of 9.64 km/sec. Its synodic period of revolution is equal to 378.09 days. In the sky Saturn appears as a yellowish star, whose brightness ranges from stellar magnitude 0 to 1 (at mean opposition). The high variability of its brightness is due to the existence of rings around the planet; the angle between the plane of the rings and the direction to the earth varies from 0° to 28°, and an observer on the earth sees the rings at different angles, which determines the variation in the planet’s brightness. The visible disk of Saturn has the shape of an ellipse, with axes of 20.7” and 14.7” (at mean opposition). At superior conjunction, the visible dimensions of Saturn are 25 percent smaller, and the brightness is 0.48 stellar magnitude fainter. Saturn’s visual albedo is equal to 0.69.

The ellipticity of Saturn’s disk is the result of a spheroidal object undergoing rapid rotation: Saturn’s period of rotation about its axis is 10 hr 14 min at the equator, 10 hr 38 min at middle latitudes, and 10 hr 40 min at a latitude of approximately 60°. The axis of rotation is inclined to the planet’s orbital plane at an angle of 63°36’. In linear units, Saturn’s equatorial radius is 60,100 km, its polar radius is 54,600 km (to an accuracy of approximately 1 percent), and its oblateness is equal to 1: 10.2. Saturn’s volume exceeds the earth’s by a factor of 770, and its mass is 95.28 times greater than the earth’s (5.68 × 1026 kg); thus, its average density is 0.7 g/cm3 (half as much as the density of the sun). With respect to the sun, Saturn’s mass is 1:3,499. The acceleration of the force of gravity on Saturn’s surface, measured at the equator, is equal to 9.54 m/sec2. The escape velocity on the planet’s surface reaches 37 km/sec.

Few details are visible on the disk of Saturn, even when the planet is viewed under optimum conditions. Only light and dark bands parallel to the equator can be seen. Dark or light patches are infrequently seen superimposed on these bands; they are useful in determining the planet’s rotation.

According to measurements of the heat flux emanating from the planet in the infrared region of the spectrum, which corresponds to the thermal flux from the sun, Saturn’s surface temperature ranges between - 190°C and - 150°C (above the equilibrium temperature of - 193°C). This indicates that the planet’s thermal radiation contains a fraction of internally generated heat, which is confirmed by measurements of the radio-frequency radiation.

The difference in Saturn’s angular rates of rotation at different latitudes indicates that the surface observed from the earth is only the outer cloud layer of the atmosphere. Some idea of the planet’s internal structure can be formed on the basis of theoretical studies. The observed perturbations in the motions of Saturn’s satellites, when compared with the planet’s oblateness and with its average density, make it possible to determine the approximate pressure and density variations in the interior (seePLANET). Saturn’s very low average density indicates that it, like the other giant planets, consists primarily of light gases—hydrogen and helium—which are also predominant on the sun. Saturn’s composition is presumed to include hydrogen (80 percent) and helium (18 percent); the heavier elements, concentrated in the planet’s core, amount to only 2 percent. To depths of about half the planet’s radius, hydrogen is found in the molecular phase; at greater depths, because of the tremendous pressures, hydrogen enters the metallic phase. At the center of Saturn the temperature is close to 20,000°K.

The chemical composition of the atmosphere above Saturn’s cloud layer is determined from the absorption lines of the planet’s spectrum. Molecular hydrogen (40 km-atmospheres) forms the principal part, methane (CH4) is indisputably present (0.35 km-atmosphere), and the existence of ammonia (NH3) is hypothesized, although it may be present in the clouds in the form of aerosols. There is reason to believe that Saturn’s atmosphere also contains helium, which is not spectroscopically detected in the spectral region accessible to us. No magnetic field has been found for Saturn.

A remarkable feature is the rings of Saturn—concentric formations of varying brightness that appear as if fitted inside each other, forming a single planar system of slight thickness lying in the planet’s equatorial plane. A ring around Saturn was first observed by Galileo in 1610, but because of the poor quality of the telescope he mistook the portions of the ring visible at the edges of the planet for satellites of Saturn. A correct description of Saturn’s ring was given by C. Huygens (1659), and soon afterward J. Cassini showed that it consisted of two concentric components—rings A and B, separated by a dark interval (Cas-sini’s division). Much later, in 1850, the American astronomer W. Bond discovered a faint, inner ring (C), and in 1969 a still fainter ring close to the planet—ring D—was detected. The brightness of ring D does not exceed 1/20 the brightness of the brightest ring—ring B. Ring A extends from 138,000 to 120,000 km above the surface of the planet; B, from 116,000 to 90,000 km; C, from 89,000 to 75,000 km; and D, from 71,000 km almost to the surface. The nature of the rings became clear after the British physicist J. Maxwell (in 1859) and the Russian mathematician S. V. Kovalevskaia (in 1885) proved by different methods that a stable ring around a planet can exist only if the ring consists of a number of individual small bodies; a continuous solid or fluid ring would be broken up by the planet’s gravitational force.

This theoretical conclusion, drawn in the late 19th century, was empirically confirmed independently by A. A. Belopol’skii (Russia), J. Keeler (USA), and H. Deslandres (France), who photographed the spectrum of Saturn by means of a slit spectrograph. They found, on the basis of the Doppler-Fizeau principle, that the outer portions of Saturn’s ring system rotate more slowly than the inner portions. The measured speed proved to be equal to the speeds Saturn’s satellites would have if they were located at the same distances from the planet.

Over a period of 29.5 years the rings of Saturn are twice visible from earth at maximum exposure, and twice there are periods when the sun and the earth are in the plane of the rings. On the latter occasions either the rings are illuminated edgewise by the sun, or they are visible edgewise to an observer on the earth. At such times, the rings are practically invisible, which indicates their very small thickness. Various investigators, relying on visual and photometric observations and on the theoretical analysis of them, draw the conclusion that the average thickness of the rings ranges from 10 cm to 10 km. Of course, a ring of such thickness cannot be seen edgewise from the earth. The dimensions of the solid bodies in the ring are estimated at 10-1 to 103 cm, with a predominance of bodies approximately 1 m in diameter. This is confirmed by the observed reflection of radio waves reflected from Saturn’s rings.

The chemical composition of the matter in the rings is apparently the same for all four sections; only the degree to which each is filled with bodies varies. The spectrum of the rings differs significantly from that of Saturn itself and from that of the sun by which the rings are illuminated. It indicates an increased reflectance of the rings in the near-infrared region (2.1 and 1.5 micrometers) corresponding to reflection from ice (H2O). It may be assumed that the bodies forming the rings either are covered with ice or frost or consist of ice. In the latter case, the mass of all the rings may be estimated at 1024 g, that is, five orders of magnitude less than the mass of the planet itself. The temperature of Saturn’s rings is apparently close to the equilibrium temperature, that is, 80°K.

Saturn has ten satellites. One of them—Titan—has dimensions comparable to those of the planets; its diameter is 5,000 km, and its mass is 2.4 × 10-4 times the mass of Saturn. Titan has an atmosphere containing methane. The satellite closest to the planet is Janus, which was discovered in 1966. It revolves around the planet in 18 hr at an average distance of 160,000 km, and its diameter is approximately 220 km. The most distant satellite is Phoebe. It revolves around Saturn in a retrograde direction at a distance of approximately 13 million km.


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Zharkov, V. N. Vnutrennee stroenie Zemli, Luny i planet. Moscow, 1973.




the name of a series of American launch vehicles developed between 1964 and 1967 for the Apollo programs; the series included the Saturn 1, Saturn 1B, and Saturn 5 models.

The Saturn 1 was an experimental, two-stage launch vehicle used for development work on certain subassemblies common to all launch vehicles and also for the orbital injection of models of the Apollo spacecraft. It had a launch weight without pay-load of 502 tons, a diameter of 6.58 m (12 m including stabilizer fins), and a length of 38.1 m. It was capable of injecting a pay-load of up to 10.2 tons into a geocentric, circular orbit with an altitude of 185 km. The propulsion system of the first stage consisted of eight liquid-propellant rocket engines, having a total thrust of 6.8 meganewtons (MN) (1 MN = 100 tons-force) and operating on liquid oxygen and kerosine. The engine of the Thor ballistic missile was the basis for these liquid-propellant rocket engines. Those on the outer edge of the installation were mounted on hinged suspensions at an angle to the axis of the rocket and were used to control the rocket through three axes. The second stage had six liquid-propellant rocket engines, having a total thrust of 40.8 kilonewtons (kN) and operating on liquid oxygen and liquid hydrogen. These engines had been used previously on the Atlas-Centaur launch vehicle. There was a total of six launchings of the Saturn 1.

The Saturn 1B was a two-stage launch vehicle designed for development work on unmanned and manned Apollo spacecraft in geocentric orbits, for the delivery of astronauts to the Skylab space station, and for spacecraft launchings in the Apollo-Soyuz program. It had a launch weight of approximately 570 tons, a diameter of 6.6 m, and a length of 43.3 m. It was capable of injecting a payload of 18.1 tons into a circular, geocentric orbit with an altitude of 195 km. The first stage used a modified first stage from the Saturn 1 and had a total thrust when operating on liquid oxygen and kerosine of 7.44 MN. The second stage had a single liquid-propellant rocket engine operating on liquid oxygen and liquid hydrogen with a thrust of 1.043 MN. In order to control the banking of the rocket, two installations were mounted on the second stage, each with three auxiliary engines, having a thrust of 680 kN and operating on nitrogen tetroxide and unsymmetrical dimethylhydrazine. There was a total of seven launchings on the Saturn 1B.

The Saturn 5 was a three-stage launch vehicle. It was designed for development work on a fully equipped Apollo spacecraft in geocentric and selenocentric orbits, as well as for the delivery of astronauts to the moon. Its launch weight was as much as 2,950 tons, its length was 85.6 m without payload and approximately 110 m with payload, and its diameter was 10.1 m (19.2 m including stabilizer fins). It was capable of injecting a payload of approximately 130 tons into a circular, geocentric orbit with an altitude of 195 km; it could launch up to 48.8 tons into a lunar trajectory. The propulsion system of the first stage comprised five liquid-propellant rocket engines, operating on liquid oxygen and kerosine and having a total thrust of 34.33 MN. The second stage had five liquid-propellant rocket engines, with a total thrust of 5.2 MN, and the third stage had one liquid-propellant rocket engine, with a thrust of 1.043 MN; the third stage was similar to the second stage of the Saturn 1B, but there were some design differences. The liquid-propellant rocket engine used liquid oxygen and liquid hydrogen.

There was a total of 12 launchings of the Saturn 5, including seven for lunar missions and one launching of the manned space station Skylab into a geocentric orbit.

The Saturns were assembled in the vertical position inside a building more than 5 km from the launching pad. The launching vehicles were assembled on the launch stand, which served as a launch pad.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


(aerospace engineering)
One of the very large launch vehicles built primarily for the Apollo program; begun by Army Ordnance but turned over to the National Aeronautics and Space Administration for the manned space flight program to the moon.
The second largest planet in the solar system (mass is 95.2 compared to earth's 1) and the sixth in the order of distance to the sun; it is visible to the naked eye as a yellowish first-magnitude star except during short periods near its conjunction with the sun; it is surrounded by a series of rings.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


the Roman god of agriculture and vegetation


1. one of the giant planets the sixth planet from the sun, around which revolve planar concentric rings (Saturn's rings) consisting of small frozen particles. The planet has at least 30 satellites. Mean distance from sun: 1425 million km; period of revolution around sun: 29.41 years; period of axial rotation: 10.23 hours; equatorial diameter and mass: 9.26 and 95.3 times that of the earth, respectively
2. a large US rocket used for launching various objects, such as a spaceprobe or an Apollo spacecraft, into space
3. the alchemical name for lead
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005