Saturn

Saturn  
Saturn imaged by the Cassini orbiter
Designations
Pronunciation i/ˈsætərn/[1]
Adjective Saturnian, Cronian
Epoch J2000.0
Aphelion
  • 1,513,325,783 km
  • 10.115 958 04 AU
Perihelion
  • 1,353,572,956 km
  • 9.048 076 35 AU
Semi-major axis
  • 1,433,449,370 km
  • 9.582 017 20 AU
Eccentricity 0.055 723 219
Orbital period
Synodic period 378.09 days[5]
Average orbital speed 9.69 km/s[5]
Mean anomaly 320.346 750°
Inclination
Longitude of ascending node 113.642 811°
Argument of perihelion 336.013 862°
Satellites ~ 200 observed (61 with secure orbits)
Physical characteristics
Equatorial radius
  • 60,268 ± 4 km[7][8]
  • 9.4492 Earths
Polar radius
  • 54,364 ± 10 km[7][8]
  • 8.5521 Earths
Flattening 0.097 96 ± 0.000 18
Surface area
  • 4.27×1010 km²[8][9]
  • 83.703 Earths
Volume
  • 8.2713×1014 km3[5][8]
  • 763.59 Earths
Mass
  • 5.6846×1026 kg[5]
  • 95.152 Earths
Mean density 0.687 g/cm3[5][8]
(less than water)
Equatorial surface gravity
Escape velocity 35.5 km/s[5][8]
Sidereal rotation
period
10.57 hours[10]
(10 hr 34 min)
Equatorial rotation velocity
  • 9.87 km/s[8]
  • 35,500 km/h
Axial tilt 26.73°[5]
North pole right ascension
  • 2h 42m 21s
  • 40.589°[7]
North pole declination 83.537°[7]
Albedo
Surface temp.
   1 bar level
   0.1 bar
min mean max
134 K[5]
84 K[5]
Apparent magnitude +1.47 to −0.24[11]
Angular diameter 14.5"–20.1"[5]
(excludes rings)
Atmosphere[5]
Scale height 59.5 km
Composition
~96% hydrogen (H2)
~3% helium
~0.4% methane
~0.01% ammonia
~0.01% hydrogen deuteride (HD)
0.000 7% ethane
Ices:
ammonia
water
ammonium hydrosulfide(NH4SH)

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god Saturn, its astronomical symbol () represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth.[12][13] While only 1/8 the average density of Earth, with its larger volume Saturn is just over 95 times more massive than Earth.[14][15][16]

Saturn's interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer.[17] Electrical current within the metallic hydrogen layer is thought to give rise to Saturn's planetary magnetic field, which is slightly weaker than Earth's and around one-twentieth the strength of Jupiter's.[18] The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h.

Saturn has a ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two[19] known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of "moonlets" within the rings. Titan, Saturn's largest and the Solar System's second largest moon, is larger than the planet Mercury and is the only moon in the Solar System to retain a substantial atmosphere.[20]

Contents

Physical characteristics

Saturn is classified as a gas giant planet because the exterior is predominantly composed of gas and it lacks a definite surface, although it may have a solid core.[21] The rotation of the planet causes it to take the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at the equator. Its equatorial and polar radii differ by almost 10%—60,268 km versus 54,364 km, respectively.[5] Jupiter, Uranus and Neptune, the other gas giants in the Solar System, are also oblate, but to a lesser extent. Saturn is the only planet of the Solar System that is less dense than water; about 30% less.[22] Although Saturn's core is considerably denser than water, the average specific density of the planet is 0.69 g/cm3 due to the gaseous atmosphere. Saturn is 95 times the mass of the Earth,[5] compared to Jupiter, which is 318 times the mass of the Earth[23] but only about 20% larger than Saturn.[24] Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System.[25]

Internal structure

Although Saturn is termed a gas giant, it is not entirely gaseous. The primary element that forms Saturn is hydrogen, which forms a non-ideal liquid when the density increases beyond 0.01 g/cm3. This density is reached at a radius containing 99.9% of Saturn's mass. The temperature, pressure and density inside the planet all rise steadily toward the core, which, in the deeper layers of the planet, cause hydrogen to transition into a metal.[25]

Though there is no direct information about Saturn's internal structure, planetary models suggest that its interior is similar to that of Jupiter, having a small rocky core surrounded by hydrogen and helium with trace amounts of various volatiles.[26] The rocky core is similar in composition to the Earth, but more dense. Examination of the gravitational moment of the planet, in combination with physical models of the interior, allowed French astronomers Didier Saumon and Tristan Guillot to place constraints on the mass of the planet's core. In 2004, they estimated that the core must be 9–22 times the mass of the Earth,[27][28] which would correspond to a diameter of about 25,000 km.[29] This is surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions into gas with increasing altitude. The outermost layer spans 1000 km and consists of an entirely gaseous atmosphere.[30][31][32]

Saturn has a very hot interior, reaching 11,700 °C at the core, and it radiates 2.5 times more energy into space than it receives from the Sun. Most of this extra energy is generated by the Kelvin–Helmholtz mechanism (slow gravitational compression), but this alone may not be sufficient to explain Saturn's heat production. An additional mechanism may be at play whereby Saturn generates some of its heat through the "raining out" of droplets of helium deep in its interior. As the droplets descend through the lower density hydrogen, the process releases heat by friction and leaves the outer layers of the planet depleted of helium.[33][34] These descending droplets may have created a helium shell surrounding the core.[26]

Atmosphere

The outer atmosphere of Saturn consists of 96.3% molecular hydrogen and 3.25% helium.[35] This proportion of helium is significantly deficient relative to the abundance of the elements in the Sun.[26] The quantity of elements heavier than helium are not known precisely, but the proportions are assumed to match the primordial abundances from the formation of the Solar System. The total mass of these elements is estimated to be 19–31 times the mass of the Earth, with a significant fraction located in Saturn's core region.[36]

Trace amounts of ammonia, acetylene, ethane, propane, phosphine and methane have been detected in the planet's atmosphere.[37][38][39] The upper clouds on Saturn are composed of ammonia crystals, while the lower level clouds appear to be composed of either ammonium hydrosulfide (NH4SH) or water.[40] Ultraviolet radiation from the Sun causes methane photolysis in the upper atmosphere, resulting in a series of hydrocarbon chemical reactions with the products being carried downward by eddies and diffusion. This photochemical cycle is modulated by Saturn's annual seasonal cycle.[39]

Cloud layers

Saturn's atmosphere exhibits a banded pattern similar to Jupiter's (the nomenclature is the same), but Saturn's bands are much fainter and are much wider near the equator. Saturn's finer cloud patterns were not observed until the Voyager flybys. Since then, Earth-based telescopy has improved to the point where regular observations can be made.[41]

The composition of the clouds varies with depth and increasing pressure. In the upper cloud layers, in the temperature range 100–160 K with pressures extending between 0.5–2 bar, are clouds of ammonia ice. Water ice clouds begin at a pressure of about 2.5 bar and extend down to 9.5 bar, where temperatures range from 185–270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure range 3–6 bar with temperatures of 290–235 K. Finally, the lower layers, where pressures are between 10–20 bar and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.[42]

Saturn's usually bland atmosphere occasionally exhibits long-lived ovals and other features common on Jupiter. In 1990 the Hubble Space Telescope observed an enormous white cloud near Saturn's equator which was not present during the Voyager encounters and in 1994, another, smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon which occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice.[43] Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020.[44]

Saturn's winds are easily among the Solar System's fastest. Voyager data indicate peak easterly winds of 500 m/s (1800 km/h).[45] In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere appeared a bright blue, similar to Uranus. The color was most likely caused by Rayleigh scattering.[46] Infrared imaging has shown that Saturn's south pole has a warm polar vortex, the only example of such a phenomenon known to date in the Solar System.[47] Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, believed to be the warmest spot on Saturn.[47]

North pole hexagonal cloud pattern

A persisting hexagonal wave pattern around the north polar vortex in the atmosphere at about 78°N was first noted in the Voyager images.[48][49] Unlike the north pole, HST imaging of the south polar region indicates the presence of a jet stream, but no strong polar vortex nor any hexagonal standing wave.[50] NASA reported in November 2006 that Cassini had observed a "hurricane-like" storm locked to the south pole that had a clearly defined eyewall.[51][52] This observation is particularly notable because eyewall clouds had not previously been seen on any planet other than Earth. For example, images from the Galileo spacecraft did not show an eyewall in the Great Red Spot of Jupiter.[53]

The straight sides of the northern polar hexagon are each approximately 13,800 km (8,600 mi) long, making them larger than the diameter of the Earth.[54] The entire structure rotates with a period of 10h 39m 24s, the same period as that of the planet's radio emissions, which is assumed to be equal to the period of rotation of Saturn's interior.[55] The hexagonal feature does not shift in longitude like the other clouds in the visible atmosphere.[56]

The pattern's origin is a matter of much speculation. Most astronomers believe it was caused by some standing-wave pattern in the atmosphere; but the hexagon might be a novel aurora. Polygonal shapes have been replicated in spinning buckets of fluid in a laboratory.[57]

Magnetosphere

Saturn has an intrinsic magnetic field that has a simple, symmetric shape—a magnetic dipole. Its strength at the equator—0.2 gauss (20 µT)—is approximately one twentieth than that of the field around Jupiter and slightly weaker than Earth's magnetic field.[18] As a result Saturn's magnetosphere is much smaller than Jupiter's.[58] When Voyager 2 entered the magnetosphere, the solar wind pressure was high and the magnetosphere extended only 19 Saturn radii, or 1.1 million km (712,000 mi),[59] although it enlarged within several hours, and remained so for about three days.[60] Most probably, the magnetic field is generated similarly to that of Jupiter—by currents in the metallic-hydrogen layer called a metallic-hydrogen dynamo.[58] This magnetosphere is efficient at deflecting the solar wind particles from the Sun. The moon Titan orbits within the outer part of Saturn's magnetosphere and contributes plasma from the ionized particles in Titan's outer atmosphere.[18] Saturn's magnetosphere, like Earth's, produces aurorae.[61]

Orbit and rotation

The average distance between Saturn and the Sun is over 1,400,000,000 km (9 AU). With an average orbital speed of 9.69 km/s,[5] it takes Saturn 10,759 Earth days (or about 29½ years),[62] to finish one revolution around the Sun.[5] The elliptical orbit of Saturn is inclined 2.48° relative to the orbital plane of the Earth.[5] Because of an eccentricity of 0.056, the distance between Saturn and the Sun varies by approximately 155,000,000 km between perihelion and aphelion,[5] which are the nearest and most distant points of the planet along its orbital path, respectively.

The visible features on Saturn rotate at different rates depending on latitude and multiple rotation periods have been assigned to various regions (as in Jupiter's case): System I has a period of 10 h 14 min 00 s (844.3°/d) and encompasses the Equatorial Zone, which extends from the northern edge of the South Equatorial Belt to the southern edge of the North Equatorial Belt. All other Saturnian latitudes have been assigned a rotation period of 10 h 38 min 25.4 s (810.76°/d), which is System II. System III, based on radio emissions from the planet in the period of the Voyager flybys, has a period of 10 h 39 min 22.4 s (810.8°/d); because it is very close to System II, it has largely superseded it.[63]

A precise value for the rotation period of the interior remains elusive. While approaching Saturn in 2004, Cassini found that the radio rotation period of Saturn had increased appreciably, to approximately 10 h 45 m 45 s (± 36 s).[64][65] In March 2007, it was found that the variation of radio emissions from the planet did not match Saturn's rotation rate. This variance may be caused by geyser activity on Saturn's moon Enceladus. The water vapor emitted into Saturn's orbit by this activity becomes charged and creates a drag upon Saturn's magnetic field, slowing its rotation slightly relative to the rotation of the planet.[66][67][67] The latest estimate of Saturn's rotation based on a compilation of various measurements from the Cassini, Voyager and Pioneer probes was reported in September 2007 is 10 hours, 32 minutes, 35 seconds.[68]

Planetary rings

The rings of Saturn (imaged here by Cassini in 2007) are the most massive and conspicuous in the Solar System.[31]
False-color UV image of Saturn's outer B and A rings; dirtier ringlets in the Cassini Division and Enke Gap show up red.

Saturn is probably best known for its system of planetary rings, which makes it the most visually remarkable object in the solar system.[31] The rings extend from 6,630 km to 120,700 km above Saturn's equator, average approximately 20 meters in thickness and are composed of 93% water ice with traces of tholin impurities and 7% amorphous carbon.[69] The particles that make up the rings range in size from specks of dust up to 10 m.[70] There are two main theories regarding the origin of the rings. One theory is that the rings are remnants of a destroyed moon of Saturn. The second theory is that the rings are left over from the original nebular material from which Saturn formed. Some ice in the central rings comes from the moon Enceladus' ice volcanoes.[71]

Beyond the main rings at a distance of 12 million km from the planet is the sparse Phoebe ring, which is tilted at an angle of 27° to the other rings and, like Phoebe, orbits in retrograde fashion.[72] Some of the moons of Saturn, including Pan and Prometheus, act as shepherd moons to confine the rings and prevent them from spreading out.[73] Pan and Atlas cause weak, linear density waves in Saturn's rings that have yielded more reliable calculations of their masses.[74]

In the past, astronomers believed the rings formed alongside the planet when it formed billions of years ago.[75] Instead, the age of these planetary rings is probably some hundreds of millions of years.[76]

Natural satellites

Saturn has at least 62 moons, 53 of which have formal names.[77] Titan, the largest, comprises more than 90% of the mass in orbit around Saturn, including the rings.[78] Saturn's second largest moon, Rhea, may have a tenuous ring system of its own,[79] along with a tenuous atmosphere.[80][81][82][83] Many of the other moons are very small: 34 are less than 10 km in diameter and another 14 less than 50 km.[84] Traditionally, most of Saturn's moons have been named after Titans of Greek mythology. Titan is the only satellite in the Solar System with a major atmosphere[85][86] in which a complex organic chemistry occurs. It is the only satellite with hydrocarbon lakes.[87][88]

Saturn's moon Enceladus has often been regarded as a potential base for microbial life.[89][90][91][92] Evidence of this life includes the satellite's salt-rich particles having an "ocean-like" composition that indicates most of Enceladus's expelled ice comes from the evaporation of liquid salt water.[93][94][95]

History of exploration

There have been three main phases in the observation and exploration of Saturn. The first era was ancient observations (such as with the naked eye), before the invention of the modern telescopes. Starting in the 17th century progressively more advanced telescopic observations from earth have been made. The other type is visitation by spacecraft, either by orbiting or flyby. In the 21st century observations continue from the earth (or earth-orbiting observatories) and from the Cassini orbiter at Saturn.

Ancient observations

Saturn has been known since prehistoric times.[96] In ancient times, it was the most distant of the five known planets in the solar system (excluding Earth) and thus a major character in various mythologies. Babylonian astronomers systematically observed and recorded the movements of Saturn.[97] In ancient Roman mythology, the god Saturnus, from which the planet takes its name, was the god of the agricultural and harvest sector.[98] The Romans considered Saturnus the equivalent of the Greek god Cronus.[98] The Greeks had made the outermost planet sacred to Cronus,[99] and the Romans followed suit.

Ptolemy, a Greek living in Alexandria,[100] observed an opposition of Saturn, which was the basis for his determination of the elements of its orbit.[101] In Hindu astrology, there are nine astrological objects, known as Navagrahas. Saturn, one of them, is known as "Shani", judges everyone based on the good and bad deeds performed in life.[98] In the 5th century CE, the Indian astronomical text Surya Siddhanta estimated the diameter of Saturn as 73,882 miles, an error of less than 1% from the currently accepted value of 74,580 miles, for which there exist several possible explanations.[102] Ancient Chinese and Japanese culture designated the planet Saturn as the earth star (土星). This was based on Five Elements which were traditionally used to classify natural elements.[103]

In ancient Hebrew, Saturn is called 'Shabbathai'.[104] Its angel is Cassiel. Its intelligence or beneficial spirit is Agiel (layga) and its spirit (darker aspect) is Zazel (lzaz). In Ottoman Turkish, Urdu and Malay, its name is 'Zuhal', derived from Arabic زحل.

European observations (17th–19th centuries)

Saturn's rings require at least a 15-mm-diameter telescope[105] to resolve and thus were not known to exist until Galileo first saw them in 1610.[106][107] He thought of them as two moons on Saturn's sides.[108][109] It was not until Christian Huygens used greater telescopic magnification that this notion was refuted. Huygens discovered Saturn's moon Titan; Giovanni Domenico Cassini later discovered four other moons: Iapetus, Rhea, Tethys and Dione. In 1675, Cassini discovered the gap now known as the Cassini Division.[110]

No further discoveries of significance were made until 1789 when William Herschel discovered two further moons, Mimas and Enceladus. The irregularly shaped satellite Hyperion, which has a resonance with Titan, was discovered in 1848 by a British team.[111]

In 1899 William Henry Pickering discovered Phoebe, a highly irregular satellite that does not rotate synchronously with Saturn as the larger moons do.[111] Phoebe was the first such satellite found and it takes more than a year to orbit Saturn in a retrograde orbit. During the early 20th century, research on Titan led to the confirmation in 1944 that it had a thick atmosphere—a feature unique among the solar system's moons.[112]

Modern NASA and ESA probes

Pioneer 11 flyby

Pioneer 11 carried out the first flyby of Saturn in September 1979, when it passed within 20,000 km of the planet's cloud tops. Images were taken of the planet and a few of its moons, although their resolution was too low to discern surface detail. The spacecraft also studied Saturn's rings, revealing the thin F-ring and the fact that dark gaps in the rings are bright when viewed at high phase angle (towards the sun), meaning that they contain fine light-scattering material. In addition, Pioneer 11 measured the temperature of Titan.[113]

Voyager flybys

In November 1980, the Voyager 1 probe visited the Saturn system. It sent back the first high-resolution images of the planet, its rings and satellites. Surface features of various moons were seen for the first time. Voyager 1 performed a close flyby of Titan, increasing knowledge of the atmosphere of the moon. It proved that Titan's atmosphere is impenetrable in visible wavelengths; so, no surface details were seen. The flyby changed the spacecraft's trajectory out from the plane of the solar system.[114]

Almost a year later, in August 1981, Voyager 2 continued the study of the Saturn system. More close-up images of Saturn's moons were acquired, as well as evidence of changes in the atmosphere and the rings. Unfortunately, during the flyby, the probe's turnable camera platform stuck for a couple of days and some planned imaging was lost. Saturn's gravity was used to direct the spacecraft's trajectory towards Uranus.[114]

The probes discovered and confirmed several new satellites orbiting near or within the planet's rings, as well as the small Maxwell Gap (a gap within the C Ring) and Keeler gap (a 42 km wide gap in the A Ring).

Cassini–Huygens spacecraft

On July 1, 2004, the Cassini–Huygens space probe performed the SOI (Saturn Orbit Insertion) maneuver and entered into orbit around Saturn. Before the SOI, Cassini had already studied the system extensively. In June 2004, it had conducted a close flyby of Phoebe, sending back high-resolution images and data.

Cassini's flyby of Saturn's largest moon, Titan, has captured radar images of large lakes and their coastlines with numerous islands and mountains. The orbiter completed two Titan flybys before releasing the Huygens probe on December 25, 2004. Huygens descended onto the surface of Titan on January 14, 2005, sending a flood of data during the atmospheric descent and after the landing.[115] Cassini has since conducted multiple flybys of Titan and other icy satellites.

Since early 2005, scientists have been tracking lightning on Saturn. The power of the lightning is approximately 1,000 times that of lightning on Earth.[116]

In 2006, NASA reported that Cassini had found evidence of liquid water reservoirs that erupt in geysers on Saturn's moon Enceladus. Images had shown jets of icy particles being emitted into orbit around Saturn from vents in the moon's south polar region. According to Andrew Ingersoll, California Institute of Technology, "Other moons in the solar system have liquid-water oceans covered by kilometers of icy crust. What's different here is that pockets of liquid water may be no more than tens of meters below the surface."[117] In May 2011, NASA scientists at an Enceladus Focus Group Conference reported that Enceladus "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it".[118][119]

Cassini photographs have led to other significant discoveries. They have revealed a previously undiscovered planetary ring, outside the brighter main rings of Saturn and inside the G and E rings. The source of this ring is believed to be the crashing of a meteoroid off two of the moons of Saturn.[120] In July 2006, Cassini images provided evidence of hydrocarbon lakes near Titan's north pole, the presence of which were confirmed in January 2007. In March 2007, additional images near Titan's north pole revealed hydrocarbon "seas", the largest of which is almost the size of the Caspian Sea.[121] In October 2006, the probe detected a 8,000 km diameter cyclone-like storm with an eyewall at Saturn's south pole.[122]

From 2004 to November 2, 2009, the probe discovered and confirmed 8 new satellites. Its primary mission ended in 2008 when the spacecraft had completed 74 orbits around the planet. The probe's mission was extended to September 2010 and then extended again to 2017, to study a full period of Saturn's seasons.[123]

Observation

Saturn is the most distant of the five planets easily visible to the naked eye, the other four being Mercury, Venus, Mars and Jupiter (Uranus and occasionally 4 Vesta are visible to the naked eye in very dark skies). It was the last planet known to early astronomers until Uranus was discovered in 1781. Saturn appears to the naked eye in the night sky as a bright, yellowish point of light whose apparent magnitude is usually between +1 and 0. It takes approximately 29½ years to make a complete circuit of the ecliptic against the background constellations of the zodiac. Most people will require optical aid (large binoculars or a telescope) magnifying at least 20× to clearly resolve Saturn's rings.[31][105]

While it is a rewarding target for observation for most of the time it is visible in the sky, Saturn and its rings are best seen when the planet is at or near opposition (the configuration of a planet when it is at an elongation of 180° and thus appears opposite the Sun in the sky). During the opposition of December 17, 2002, Saturn appeared at its brightest due to a favorable orientation of its rings relative to the Earth,[124] even though Saturn was closer to the Earth and Sun in late 2003.[124]

In culture

See also


References

  1. ^ Walter, Elizabeth (April 21, 2003). Cambridge Advanced Learner's Dictionary (Second ed.). Cambridge University Press. ISBN 978-0-521-53106-1. 
  2. ^ Yeomans, Donald K. (2006-07-13). "HORIZONS System". NASA JPL. Archived from the original on 2007-06-25. http://ssd.jpl.nasa.gov/?horizons. Retrieved 2007-08-08. —At the site, go to the "web interface" then select "Ephemeris Type: ELEMENTS", "Target Body: Saturn Barycenter" and "Center: Sun".
  3. ^ Orbital elements refer to the barycenter of the Saturn system and are the instantaneous osculating values at the precise J2000 epoch. Barycenter quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis from to the motion of the moons.
  4. ^ Seligman, Courtney. "Rotation Period and Day Length". Archived from the original on 2011-08-10. http://cseligman.com/text/sky/rotationvsday.htm. Retrieved 2009-08-13. 
  5. ^ a b c d e f g h i j k l m n o p q r s Williams, David R. (September 7, 2006). "Saturn Fact Sheet". NASA. Archived from the original on 2011-08-21. http://nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.html. Retrieved 2007-07-31. 
  6. ^ "The MeanPlane (Invariable plane) of the Solar System passing through the barycenter". 2009-04-03. Archived from the original on 2009-05-14. http://home.comcast.net/~kpheider/MeanPlane.gif. Retrieved 2009-04-10.  (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane)
  7. ^ a b c d Seidelmann, P. Kenneth; Archinal, B. A.; A'hearn, M. F. et al. (2007). "Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006". Celestial Mechanics and Dynamical Astronomy 98 (3): 155–180. Bibcode 2007CeMDA..98..155S. doi:10.1007/s10569-007-9072-y.  edit
  8. ^ a b c d e f g h Refers to the level of 1 bar atmospheric pressure
  9. ^ "NASA: Solar System Exploration: Planets: Saturn: Facts & Figures". Solarsystem.nasa.gov. 2011-03-22. Archived from the original on 2011-10-05. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn&Display=Facts. Retrieved 2011-08-08. 
  10. ^ 'Astronews' (New Spin For Saturn). Astronomy. November 2009. p. 23. 
  11. ^ Schmude, Richard W. Junior (2001). "Wideband photoelectric magnitude measurements of Saturn in 2000". Georgia Journal of Science. http://findarticles.com/p/articles/mi_qa4015/is_200101/ai_n8933308. Retrieved 2007-10-14. 
  12. ^ Brainerd, Jerome James (November 24, 2004). "Characteristics of Saturn". The Astrophysics Spectator. Archived from the original on 2011-10-05. http://www.astrophysicsspectator.com/tables/Saturn.html. Retrieved 2010-07-05. 
  13. ^ "General Information About Saturn". Scienceray. July 28, 2011. Archived from the original on 2011-10-05. http://scienceray.com/astronomy/general-information-about-saturn-2/1/. Retrieved 2011-08-17. 
  14. ^ Brainerd, Jerome James (October 6, 2004). "Solar System Planets Compared to Earth". The Astrophysics Spectator. Archived from the original on 2011-10-05. http://www.astrophysicsspectator.com/tables/PlanetComparativeData.html. Retrieved 2010-07-05. 
  15. ^ Dunbar, Brian (November 29, 2007). "NASA – Saturn". NASA. Archived from the original on 2011-10-05. http://mynasa.nasa.gov/worldbook/saturn_worldbook.html. Retrieved 2011-07-21. 
  16. ^ Cain, Fraser (July 3, 2008). "Mass of Saturn". Universe Today. http://www.universetoday.com/15378/mass-of-saturn/. Retrieved 2011-08-17. 
  17. ^ Brainerd, Jerome James (October 27, 2004). "Giant Gaseous Planets". The Astrophysics Spectator. Archived from the original on 2011-10-05. http://www.astrophysicsspectator.com/topics/planets/GiantGaseousPlanets.html. Retrieved 2010-07-05. 
  18. ^ a b c Russell, C. T.; Luhmann, J. G. (1997). "Saturn: Magnetic Field and Magnetosphere". UCLA – IGPP Space Physics Center. Archived from the original on 2011-10-05. http://www-ssc.igpp.ucla.edu/personnel/russell/papers/sat_mag.html. Retrieved 2007-04-29. 
  19. ^ Piazza, Enrico. "Saturn's Moons". Cassini, Equinox Mission. JPL NASA. Archived from the original on 2011-10-05. http://saturn.jpl.nasa.gov/science/moons/. Retrieved 2010-06-22. 
  20. ^ Munsell, Kirk (April 6, 2005). "The Story of Saturn". NASA Jet Propulsion Laboratory; California Institute of Technology. Archived from the original on 2011-08-22. http://saturn.jpl.nasa.gov/news/features/saturn-story/moons.cfm. Retrieved 2007-07-07. 
  21. ^ Melosh, H. Jay (2011). Planetary Surface Processes. Cambridge Planetary Science. 13. Cambridge University Press. p. 5. ISBN 0521514185. http://books.google.com/books?id=3bQD1DJgliIC&pg=PA5. 
  22. ^ "Saturn – The Most Beautiful Planet of our solar system". Preserve Articles. January 23, 2011. Archived from the original on 2011-10-05. http://www.preservearticles.com/201101233659/saturn-the-most-beautiful-planet-of-our-solar-system.html. Retrieved 2011-07-24. 
  23. ^ Williams, David R. (November 16, 2004). "Jupiter Fact Sheet". NASA. Archived from the original on 2011-10-05. http://nssdc.gsfc.nasa.gov/planetary/factsheet/jupiterfact.html. Retrieved 2007-08-02. 
  24. ^ "Jupiter compared to Saturn". NASA. Archived from the original on July 14, 2007. http://web.archive.org/web/20070714064141/http://ase.arc.nasa.gov/projects/bayes-group/Atlas/size/Jupiter/Saturn.html. Retrieved 2007-07-15. 
  25. ^ a b Fortney, Jonathan J.; Nettelmann, Nadine (May 2010), "The Interior Structure, Composition, and Evolution of Giant Planets", Space Science Reviews 152 (1-4): 423–447, Bibcode 2010SSRv..152..423F, doi:10.1007/s11214-009-9582-x 
  26. ^ a b c Guillot, Tristan et al. (2009). "Saturn's Exploration Beyond Cassini-Huygens". In Dougherty, Michele K.; Esposito, Larry W.; Krimigis, Stamatios M.,. Saturn from Cassini-Huygens. Springer Science+Business Media B.V.. p. 745. arXiv:0912.2020. Bibcode 2009sfch.book..745G. doi:10.1007/978-1-4020-9217-6_23. ISBN 978-1-4020-9216-9. 
  27. ^ Fortney, Jonathan J. (2004). "Looking into the Giant Planets". Science 305 (5689): 1414–1415. doi:10.1126/science.1101352. PMID 15353790. 
  28. ^ Saumon, D.; Guillot, T. (July 2004). "Shock Compression of Deuterium and the Interiors of Jupiter and Saturn". The Astrophysical Journal 609 (2): 1170–1180. Bibcode 2004ApJ...609.1170S. doi:10.1086/421257. 
  29. ^ "Saturn". BBC. 2000. Archived from the original on 2011-08-21. http://www.bbc.co.uk/dna/h2g2/A383960. Retrieved 2011-07-19. 
  30. ^ Faure, Gunter; Mensing, Teresa M. (2007). Introduction to planetary science: the geological perspective. Springer. p. 337. ISBN 1-4020-5233-2. http://books.google.com/books?id=U4FZp6f6q6MC&pg=PA337. 
  31. ^ a b c d "Saturn". National Maritime Museum. Archived from the original on 2011-10-05. http://www.nmm.ac.uk/server/show/conWebDoc.286. Retrieved 2007-07-06. 
  32. ^ "Structure of Saturn's Interior". Windows to the Universe. Archived from the original on 2011-08-21. http://www.windows2universe.org/saturn/interior/S_int_structure_overview.html. Retrieved 2011-07-19. 
  33. ^ de Pater, Imke; Lissauer, Jack J. (2010). Planetary Sciences (2nd ed.). Cambridge University Press. pp. 254–255. ISBN 0-521-85371-0. http://books.google.com/books?id=a_ijoTgDhnEC&pg=PA254. 
  34. ^ "NASA – Saturn". NASA. 2004. Archived from the original on 2011-08-21. http://www.nasa.gov/worldbook/saturn_worldbook.html. Retrieved 2007-07-27. 
  35. ^ Saturn. Universe Guide. Retrieved 29 March 2009.
  36. ^ Guillot, Tristan (1999). "Interiors of Giant Planets Inside and Outside the Solar System". Science 286 (5437): 72–77. Bibcode 1999Sci...286...72G. doi:10.1126/science.286.5437.72. PMID 10506563. 
  37. ^ Courtin, R. et al. (1967). "The Composition of Saturn's Atmosphere at Temperate Northern Latitudes from Voyager IRIS spectra". Bulletin of the American Astronomical Society 15: 831. Bibcode 1983BAAS...15..831C. 
  38. ^ Cain, Fraser (January 22, 2009). "Atmosphere of Saturn". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/24029/atmosphere-of-saturn/. Retrieved 2011-07-20. 
  39. ^ a b Guerlet, S.; Fouchet, T.; Bézard, B. (November 2008), "Ethane, acetylene and propane distribution in Saturn's stratosphere from Cassini/CIRS limb observations", in Combes, C., SF2A-2008: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, p. 405, Bibcode 2008sf2a.conf..405G 
  40. ^ Martinez, Carolina (September 5, 2005). "Cassini Discovers Saturn's Dynamic Clouds Run Deep". NASA. Archived from the original on 2011-10-05. http://www.nasa.gov/mission_pages/cassini/whycassini/cassini-090505-clouds.html. Retrieved 2007-04-29. 
  41. ^ Orton, Glenn S. (September 2009). "Ground-Based Observational Support for Spacecraft Exploration of the Outer Planets". Earth, Moon, and Planets 105 (2–4): 143–152. Bibcode 2009EM&P..105..143O. doi:10.1007/s11038-009-9295-x. 
  42. ^ Dougherty, Krimigis; Larry, Esposito (2009), Saturn from Cassini-Huygens, Springer, p. 162, ISBN 1402092164, http://books.google.com/books?id=M56CHHxVMP4C&pg=PA162 
  43. ^ Pérez-Hoyos, S.; Sánchez-Laveg, A.; French, R. G.; J. F., Rojas (2005). "Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994–2003)". Icarus 176 (1): 155–174. Bibcode 2005Icar..176..155P. doi:10.1016/j.icarus.2005.01.014. 
  44. ^ Patrick Moore, ed., 1993 Yearbook of Astronomy, (London: W.W. Norton & Company, 1992), Mark Kidger, "The 1990 Great White Spot of Saturn", pp. 176–215.
  45. ^ Hamilton, Calvin J. (1997). "Voyager Saturn Science Summary". Solarviews. Archived from the original on 2011-10-05. http://www.solarviews.com/eng/vgrsat.htm. Retrieved 2007-07-05. 
  46. ^ Watanabe, Susan (March 27, 2007). "Saturn's Strange Hexagon". NASA. Archived from the original on 2010-02-01. http://www.nasa.gov/mission_pages/cassini/multimedia/pia09188.html. Retrieved 2007-07-06. 
  47. ^ a b "Warm Polar Vortex on Saturn". Merrillville Community Planetarium. 2007. Archived from the original on 2011-10-05. http://www.mcpstars.org/node/353. Retrieved 2007-07-25. 
  48. ^ Godfrey, D. A. (1988). "A hexagonal feature around Saturn's North Pole". Icarus 76 (2): 335. Bibcode 1988Icar...76..335G. doi:10.1016/0019-1035(88)90075-9. 
  49. ^ Sanchez-Lavega, A.; Lecacheux, J.; Colas, F.; Laques, P. (1993). "Ground-based observations of Saturn's north polar SPOT and hexagon". Science 260 (5106): 329–32. Bibcode 1993Sci...260..329S. doi:10.1126/science.260.5106.329. PMID 17838249. 
  50. ^ "Hubble Space Telescope Observations of the Atmospheric Dynamics in Saturn's South Pole from 1997 to 2002". The American Astronomical Society. October 8, 2002. http://www.aas.org/publications/baas/v34n3/dps2002/10.htm. Retrieved 2007-07-06. 
  51. ^ "NASA catalog page for image PIA09187". NASA Planetary Photojournal. Archived from the original on 2011-10-05. http://photojournal.jpl.nasa.gov/catalog/PIA09187. Retrieved 2007-05-23. 
  52. ^ "Huge 'hurricane' rages on Saturn". BBC News. November 10, 2006. Archived from the original on 2011-10-05. http://news.bbc.co.uk/2/hi/6135450.stm?lsm. Retrieved 2011-09-29. 
  53. ^ "NASA Sees into the Eye of a Monster Storm on Saturn". NASA. November 9, 2006. Archived from the original on 2011-10-05. http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=703. Retrieved 2006-11-20. 
  54. ^ "New images show Saturn's weird hexagon cloud". MSNBC. December 12, 2009. Archived from the original on 2011-10-05. http://www.msnbc.msn.com/id/34352533/ns/technology_and_science-space/t/new-images-show-saturns-weird-hexagon-cloud/. Retrieved 2011-09-29. 
  55. ^ Godfrey, D. A. (March 9, 1990). "The Rotation Period of Saturn's Polar Hexagon". Science 247 (4947): 1206–1208. doi:10.1126/science.247.4947.1206. PMID 17809277. 
  56. ^ Baines, Kevin H. et al. (December 2009). "Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS". Planetary and Space Science 57 (14–15): 1671–1681. Bibcode 2009P&SS...57.1671B. doi:10.1016/j.pss.2009.06.026. 
  57. ^ Ball, Philip (May 19, 2006). "Geometric whirlpools revealed". Nature. doi:10.1038/news060515-17.  Bizarre geometric shapes that appear at the centre of swirling vortices in planetary atmospheres might be explained by a simple experiment with a bucket of water but correlating this to Saturn's pattern is by no means certain.
  58. ^ a b McDermott, Matthew (2000). "Saturn: Atmosphere and Magnetosphere". Thinkquest Internet Challenge. Archived from the original on 2011-10-05. http://library.thinkquest.org/C005921/Saturn/satuAtmo.htm. Retrieved 2007-07-15. 
  59. ^ "Voyager – Saturn's Magnetosphere". NASA Jet Propulsion Laboratory. October 18, 2010. Archived from the original on 2011-10-05. http://voyager.jpl.nasa.gov/science/saturn_magnetosphere.html. Retrieved 2011-07-19. 
  60. ^ Atkinson, Nancy (December 14, 2010). "Hot Plasma Explosions Inflate Saturn's Magnetic Field". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/81713/hot-plasma-explosions-inflate-saturns-magnetic-field/. Retrieved 2011-08-24. 
  61. ^ Russell, Randy (June 3, 2003). "Saturn Magnetosphere Overview". Windows to the Universe. Archived from the original on 2011-10-05. http://www.windows2universe.org/saturn/upper_atmosphere.html. Retrieved 2011-07-19. 
  62. ^ Cain, Fraser (January 26, 2009). "Orbit of Saturn". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/24168/orbit-of-saturn/. Retrieved 2011-07-19. 
  63. ^ Benton, Julius (2006). Saturn and how to observe it. Astronomers' observing guides (11th ed.). Springer Science & Business. p. 136. ISBN 1-85233-887-3. http://books.google.com/books?id=779fPuQmWeYC&pg=PA136. 
  64. ^ "Scientists Find That Saturn's Rotation Period is a Puzzle". NASA. June 28, 2004. Archived from the original on 2011-08-21. http://www.nasa.gov/mission_pages/cassini/media/cassini-062804.html. Retrieved 2007-03-22. 
  65. ^ Cain, Fraser. "Saturn." Universe Today. 30 June 2008. Retrieved 17 August 2011. Archived 5 October 2011 at WebCite
  66. ^ "Enceladus Geysers Mask the Length of Saturn's Day" (Press release). NASA Jet Propulsion Laboratory. March 22, 2007. http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=733. Retrieved 2007-03-22.  Archived 5 October 2011 at WebCite
  67. ^ a b Gurnett, D. A. et al. (2007). "The Variable Rotation Period of the Inner Region of Saturn's Plasma Disc". Science 316 (5823): 442–5. Bibcode 2007Sci...316..442G. doi:10.1126/science.1138562. PMID 17379775. 
  68. ^ Anderson, J. D.; Schubert, G. (2007). "Saturn's gravitational field, internal rotation and interior structure". Science 317 (5843): 1384–1387. Bibcode 2007Sci...317.1384A. doi:10.1126/science.1144835. PMID 17823351. 
  69. ^ Poulet F.; Cuzzi J.N. (2002). "The Composition of Saturn's Rings". Icarus 160 (2): 350. Bibcode 2002Icar..160..350P. doi:10.1006/icar.2002.6967. 
  70. ^ Shafiq, Muhammad (2005). "Dusty Plasma Response to a Moving Test Change" (PDF). http://www.ee.kth.se/php/modules/publications/reports/2005/TRITA-ALP-2005-03.pdf. Retrieved 2007-07-25. 
  71. ^ Spahn, F. et al. (2006). "Cassini Dust Measurements at Enceladus and Implications for the Origin of the E Ring". Science 311 (5766): 1416–1418. Bibcode 2006Sci...311.1416S. doi:10.1126/science.1121375. PMID 16527969. 
  72. ^ Cowen, Rob (November 7, 2999). "Largest known planetary ring discovered". Science News. Archived from the original on 2011-10-05. http://www.sciencenews.org/view/generic/id/48097/title/Largest_known_planetary_ring_discovered. Retrieved 2010-04-09. 
  73. ^ Russell, Randy (June 7, 2004). "Saturn Moons and Rings". Windows to the Universe. Archived from the original on 2011-10-05. http://www.windows2universe.org/saturn/moons_and_rings.html. Retrieved 2011-07-19. 
  74. ^ NASA Jet Propulsion Laboratory (March 3, 2005). "NASA's Cassini Spacecraft Continues Making New Discoveries". ScienceDaily. Archived from the original on 2011-10-05. http://www.sciencedaily.com/releases/2005/02/050225110106.htm. Retrieved July 19, 2011. 
  75. ^ "The Real Lord of the Rings". Science@NASA. February 12, 2002. Archived from the original on 2011-10-05. http://science1.nasa.gov/science-news/science-at-nasa/2002/12feb_rings/. Retrieved August 24, 2011. 
  76. ^ "Age and Fate of Saturn's Rings" (PD). Creation Concepts. http://creationconcepts.org/resources/RINGS.pdf. Retrieved 2011-07-23. 
  77. ^ Wall, Mike (June 21, 2011). "Saturn's 'Ice Queen' Moon Helene Shimmers in New Photo". Space.com. Archived from the original on 2011-10-05. http://www.space.com/12032-saturn-moon-helene-photo-cassini.html. Retrieved 2011-07-19. 
  78. ^ Brunier, Serge (2005). Solar System Voyage. Cambridge University Press. p. 164. ISBN 978-0-521-80724-1. 
  79. ^ Jones, G. H. et al. (March 7, 2008). "The Dust Halo of Saturn's Largest Icy Moon, Rhea". Science 319 (5868): 1380–1384. Bibcode 2008Sci...319.1380J. doi:10.1126/science.1151524. PMID 18323452. 
  80. ^ Atkinson, Nancy (November 26, 2010). "Tenuous Oxygen Atmosphere Found Around Saturn's Moon Rhea". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/8023/tenuous-oxygen-atmosphere-found-around-saturns-moon-rhea/. Retrieved 2011-07-20. 
  81. ^ NASA (November 30, 2010). "Thin air: Oxygen atmosphere found on Saturn's moon Rhea". ScienceDaily. Archived from the original on 2011-10-05. http://www.sciencedaily.com/releases/2010/11/101128222041.htm. Retrieved 2011-07-23. 
  82. ^ "Oxygen found on Saturn moon: NASA spacecraft discovers Rhea has thin atmosphere rich in O2". Daily Mail. November 26, 2010. Archived from the original on 2011-10-05. http://www.dailymail.co.uk/sciencetech/article-1333294/Oxygen-Saturn-moon-Nasa-spacecraft-discovers-Rhea-atmosphere-rich-O2.html. Retrieved 2011-07-23. 
  83. ^ Ryan, Clare (November 26, 2010). "Cassini reveals oxygen atmosphere of Saturn′s moon Rhea". UCL Mullard Space Science Laboratory. Archived from the original on 2011-10-05. http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20101126.html. Retrieved 2011-07-23. 
  84. ^ "Saturn's Known Satellites". Department of Terrestrial Magnetism. Archived from the original on 2011-10-05. http://www.dtm.ciw.edu/users/sheppard/satellites/satsatdata.html. Retrieved 2010-06-22. 
  85. ^ "Cassini Finds Hydrocarbon Rains May Fill Titan Lakes". ScienceDaily. January 30, 2009. Archived from the original on 2011-10-05. http://www.sciencedaily.com/releases/2009/01/090129182514.htm. Retrieved 2011-07-19. 
  86. ^ "Voyager – Titan". NASA Jet Propulsion Laboratory. October 18, 2010. Archived from the original on 2011-10-05. http://voyager.jpl.nasa.gov/science/saturn_titan.html. Retrieved 2011-07-19. 
  87. ^ "Evidence of hydrocarbon lakes on Titan". Associated Press. MSNBC. July 25, 2006. Archived from the original on 2011-10-05. http://www.msnbc.msn.com/id/14029488/ns/technology_and_science-space/t/evidence-hydrocarbon-lakes-titan/. Retrieved July 19, 2011. 
  88. ^ "Hydrocarbon lake finally confirmed on Titan". Cosmos Magazine. July 31, 2008. Archived from the original on 2011-10-05. http://www.cosmosmagazine.com/news/2109/ethane-lake-finally-confirmed-titan. Retrieved 2011-07-19. 
  89. ^ NASA (April 21, 2008). "Could There Be Life On Saturn's Moon Enceladus?". ScienceDaily. Archived from the original on 2011-10-05. http://www.sciencedaily.com/releases/2008/04/080420122601.htm. Retrieved 2011-07-19. 
  90. ^ Madrigal, Alexis (June 24, 2009). "Hunt for Life on Saturnian Moon Heats Up". Wired Science. Archived from the original on 2011-10-05. http://www.wired.com/wiredscience/2009/06/enceladusocean/. Retrieved July 19, 2011. 
  91. ^ Spotts, Peter N. (September 28, 2005). "Life beyond Earth? Potential solar system sites pop up". USA Today. Archived from the original on 2011-10-05. http://www.usatoday.com/tech/science/space/2005-09-28-solar-system-life_x.htm. Retrieved July 21, 2011. 
  92. ^ Pili, Unofre (September 9, 2009). "Enceladus: Saturn′s Moon, Has Liquid Ocean of Water". Scienceray. Archived from the original on 2011-10-05. http://scienceray.com/astronomy/enceladus-saturns-moon-has-liquid-ocean-of-water/. Retrieved 2011-07-21. 
  93. ^ "Strongest evidence yet indicates Enceladus hiding saltwater ocean". Physorg. June 22, 2011. Archived from the original on 2011-10-05. http://www.physorg.com/news/2011-06-strongest-evidence-icy-saturn-moon.html. Retrieved 2011-07-19. 
  94. ^ Kaufman, Marc (June 22, 2011). "Saturn′s moon Enceladus shows evidence of an ocean beneath its surface". Washington Post. Archived from the original on 2011-10-05. http://www.washingtonpost.com/national/health-science/saturns-moon-enceladus-shows-evidence-of-an-ocean-beneath-its-surface/2011/06/22/AGWYaPgH_story.html. Retrieved 2011-07-19. 
  95. ^ Greicius, Tony; Dunbar, Brian (June 22, 2011). "Cassini Captures Ocean-Like Spray at Saturn Moon". NASA. Archived from the original on 2011-10-05. http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20110622.html. Retrieved 2011-09-17. 
  96. ^ "Saturn > Observing Saturn". National Maritime Museum. http://www.nmm.ac.uk/server/show/conWebDoc.13852/viewPage/5. Retrieved 2007-07-06. 
  97. ^ Sachs, A. (May 2, 1974). "Babylonian Observational Astronomy". Philosophical Transactions of the Royal Society of London (Royal Society of London) 276 (1257): 43–50 [45 & 48–9]. Bibcode 1974RSPTA.276...43S. doi:10.1098/rsta.1974.0008. JSTOR 74273. 
  98. ^ a b c "Starry Night Times". Imaginova Corp.. 2006. Archived from the original on 2011-08-21. http://www.starrynight.com/sntimes/2006/2006-01-full.html. Retrieved 2007-07-05. 
  99. ^ Evans, James (1998). The History and Practice of Ancient Astronomy. Oxford University Press. pp. 296–7. ISBN 978-0-19-509539-5. 
  100. ^ Harland, David Michael (2007). Cassini at Saturn: Huygens results. p. 1. ISBN 978-0-387-26129-4. http://books.google.com/books?id=ScORNbV0E8wC&pg=PA1. 
  101. ^ Staff (April 1893). "Superstitions about Saturn". The Popular Science Monthly: 862. http://books.google.com/books?id=cSADAAAAMBAJ&pg=PA862. 
  102. ^ Thompson, Richard (1997). "Planetary Diameters in the Surya-Siddhanta". Journal of Scientific Exploration 11 (2): 193–200 [193–6]. http://www.scientificexploration.org/journal/jse_11_2_thompson.pdf. Retrieved 2010-03-13. 
  103. ^ China: De Groot, Jan Jakob Maria (1912). Religion in China: universism. a key to the study of Taoism and Confucianism. 10. G. P. Putnam's Sons. p. 300. http://books.google.com/books?id=ZAaP7dyjCrAC&pg=PA300. Retrieved 2010-01-08. 
    Japan: Crump, Thomas (1992). The Japanese numbers game: the use and understanding of numbers in modern Japan. Routledge. pp. 39–40. ISBN 0415056098. 
    Korea: Hulbert, Homer Bezaleel (1909). The passing of Korea. Doubleday, Page & company. p. 426. http://books.google.com/books?id=fxwpAAAAYAAJ&pg=PA426. Retrieved 2010-01-08. 
  104. ^ Cessna, Abby (November 15, 2009). "When Was Saturn Discovered?". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/45087/when-was-saturn-discovered/. Retrieved July 21, 2011. 
  105. ^ a b Eastman, Jack (1998). "Saturn in Binoculars". The Denver Astronomical Society. Archived from the original on 2011-08-21. http://www.thedas.org/dfiles/eastman_saturn.html. Retrieved 2008-09-03. 
  106. ^ Chan, Gary (2000). "Saturn: History Timeline". Archived from the original on 2011-08-21. http://library.thinkquest.org/C005921/Saturn/satuHist.htm. Retrieved 2007-07-16. 
  107. ^ Cain, Fraser (2008-07-03). "History of Saturn". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/15390/history-of-saturn/. Retrieved 2011-07-24. 
  108. ^ Cain, Fraser (July 7, 2008). "Interesting Facts About Saturn". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/15418/interesting-facts-about-saturn/. Retrieved September 17, 2011. 
  109. ^ Cain, Fraser (2009-11-27). "Who Discovered Saturn?". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/46237/who-discovered-saturn/. Retrieved 2011-09-17. 
  110. ^ Micek, Catherine. "Saturn: History of Discoveries". Archived from the original on 2011-08-21. http://huygensgcms.gsfc.nasa.gov/Shistory.htm. Retrieved 2007-07-15. 
  111. ^ a b Barton, Samuel G. (April 1946). "The names of the satellites". Popular Astronomy 54: 122–130. Bibcode 1946PA.....54..122B. 
  112. ^ Kuiper, Gerard P. (November 1944). "Titan: a Satellite with an Atmosphere". Astrophysical Journal 100: 378–388. Bibcode 1944ApJ...100..378K. doi:10.1086/144679. 
  113. ^ "The Pioneer 10 & 11 Spacecraft". Mission Descriptions. Archived from the original on 2006-01-30. http://web.archive.org/web/20060130100401/http://spaceprojects.arc.nasa.gov/Space_Projects/pioneer/PN10&11.html. Retrieved 2007-07-05. 
  114. ^ a b "Missions to Saturn". The Planetary Society. 2007. Archived from the original on 2011-08-21. http://www.planetary.org/explore/topics/saturn/missions.html. Retrieved 2007-07-24. 
  115. ^ Lebreton, Jean-Pierre et al. (December 2005). "An overview of the descent and landing of the Huygens probe on Titan". Nature 438 (7069): 758–764. Bibcode 2005Natur.438..758L. doi:10.1038/nature04347. PMID 16319826. 
  116. ^ "Astronomers Find Giant Lightning Storm At Saturn". ScienceDaily LLC. 2007. Archived from the original on 2011-08-21. http://www.sciencedaily.com/releases/2006/02/060215090726.htm. Retrieved 2007-07-27. 
  117. ^ Pence, Michael (March 9, 2006). "NASA's Cassini Discovers Potential Liquid Water on Enceladus". NASA Jet Propulsion Laboratory. Archived from the original on 2011-08-21. http://www.nasa.gov/mission_pages/cassini/media/cassini-20060309.html. Retrieved 2011-06-03. 
  118. ^ Lovett, Richard A. (May 31, 2011). "Enceladus named sweetest spot for alien life". Nature (Nature). doi:10.1038/news.2011.337. Archived from the original on 2011-10-05. http://www.nature.com/news/2011/110531/full/news.2011.337.html. Retrieved 2011-06-03. 
  119. ^ Kazan, Casey (June 2, 2011). "Saturn's Enceladus Moves to Top of "Most-Likely-to-Have-Life" List". The Daily Galaxy. Archived from the original on 2011-08-21. http://www.dailygalaxy.com/my_weblog/2011/06/saturns-enceladus-moves-to-top-of-most-likely-to-have-life-list.html. Retrieved 2011-06-03. 
  120. ^ Shiga, David (September 20, 2007). "Faint new ring discovered around Saturn". NewScientist.com. Archived from the original on 2011-08-21. http://space.newscientist.com/channel/solar-system/cassini-huygens/dn10124-faint-new-ring-discovered-around-saturn.html. Retrieved 2007-07-08. 
  121. ^ "Probe reveals seas on Saturn moon". BBC. March 14, 2007. Archived from the original on 2011-10-05. http://news.bbc.co.uk/2/hi/science/nature/6449081.stm. Retrieved 2007-09-26. 
  122. ^ Rincon, Paul (November 10, 2006). "Huge 'hurricane' rages on Saturn". BBC. Archived from the original on 2011-10-05. http://news.bbc.co.uk/2/hi/science/nature/6135450.stm. Retrieved 2007-07-12. 
  123. ^ "Mission overview – introduction". Cassini Solstice Mission. NASA / JPL. 2010. Archived from the original on 2011-08-21. http://saturn.jpl.nasa.gov/mission/introduction/. Retrieved 2010-11-23. 
  124. ^ a b Schmude, Richard W Jr (2003). "Saturn in 2002–03". Georgia Journal of Science. http://findarticles.com/p/articles/mi_qa4015/is_200301/ai_n9338203. Retrieved 2007-10-14. 
  125. ^ Bilstein, Roger E. (1999). Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicle. DIANE Publishing. p. 37. ISBN 0-7881-8186-6. http://books.google.com/books?id=JnoZTbVLx0MC&pg=PA37. 
  126. ^ Plotner, Tammy (February 22, 2008). "Time to Observe Saturn – Opposition Occurs February 23!". Universe Today. Archived from the original on 2011-10-05. http://www.universetoday.com/12926/time-to-observe-saturn-opposition-occurs-february-23/. Retrieved 2011-07-19. 
  127. ^ Reis, Ricardo Cardoso; Jones, Jane H.. "Saturn: The Ringed Planet" (PDF). IAU. http://www.astronomy2009.org/static/archives/presentations/pdf/saturn_gn.pdf. Retrieved 2011-07-23. 

Further reading

External links