The full set of rings, photographed as Saturn eclipsed the sun from the vantage of the Cassini spacecraft on September 15, 2006 (brightness has been exaggerated in this image). Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Events 668 - Eastern Roman Emperor Constans II is assassinated in his bath at Syracuse Italy. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar.

In this image of Saturn taken by the Hubble Space Telescope's ACS on March 22, 2004, the B Ring is the inner of the two wide rings, the A Ring is the outer, and the Cassini Division is the dark band between them. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into The Advanced Camera for Surveys (ACS is a third generation axial instrument aboard the Hubble Space Telescope (HST Events 238 - Gordian I and his son Gordian II are proclaimed Roman emperor. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " (The less prominent C Ring is also visible just inside the B Ring. )

The unilluminated side of Saturn's rings viewed from Cassini on May 9, 2007

The rings of Saturn are a system of planetary rings around the planet Saturn. A planetary ring is a ring of Cosmic dust and other small particles Orbiting around a Planet in a flat disc-shaped region They consist of countless small particles, ranging in size from microns to meters, that form clumps that in turn orbit about Saturn. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star The ring particles are made almost entirely of water ice, with some contamination from dust and other chemicals. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Dust is a general name for minute Solid particles with Diameters less than 500 micrometers.

Although reflection from the rings increases Saturn's brightness, they are not visible from Earth with unaided vision. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value The naked eye is a Figure of speech referring to human Visual perception that is unaided by enhancing equipment such as a Telescope or In 1610, the year he first turned a telescope to the sky, Galileo Galilei became the very first person to observe Saturn's rings, though he could not see them well enough to discern their true nature. A telescope is an instrument designed for the observation of remote objects and the collection of Electromagnetic radiation. Galileo Galilei (15 February 1564 &ndash 8 January 1642 was a Tuscan ( Italian) Physicist, Mathematician, Astronomer, and Philosopher In 1655, Christiaan Huygens was the first person to describe them as a disk surrounding Saturn. Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch ^[1]

Although many people think of Saturn's rings as being made up of "countless tiny ringlets" (a concept that goes back to Laplace), true gaps are few in number. It is more correct to think of the rings as an annular disk with concentric local maxima and minima in density and brightness. In Mathematics, an annulus (the Latin word for "little ring" with plural annuli) is a ring-shaped geometric figure or more generally a term Concentric objects share the same center, axis or origin with one inside the other In Mathematics, maxima and minima, known collectively as extrema, are the largest value (maximum or smallest value (minimum that On the scale of the clumps within the rings there is a lot of empty space, but in general these empty spaces are discontinuous.

There are several gaps within the rings: two opened by known moons embedded within them, and many others at locations of known destabilizing orbital resonances with Saturn's moons. In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their Saturn has 60 confirmed moons. These include 22 regular satellites, which all have Prograde orbits that are not greatly inclined with respect Other gaps remain unexplained. Stabilizing resonances, on the other hand, are responsible for the longevity of several rings, such as the Titan Ringlet and the G Ring.

Formation of Saturn's rings

A 2007 artist impression of the aggregates of icy particles that form the 'solid' portions of Saturn's rings. These elongated clumps are continually forming and dispersing. The largest particles are a few meters across.

Saturn's rings may be very old, dating to the formation of Saturn itself. It seems likely that they are composed of debris from the disruption of a moon about 300 km in diameter, bigger than Mimas. TemplateInfobox Planet. --> Mimas (ˈmaɪməs, or as Greek The last time there were collisions large enough to be likely to disrupt a moon that large was during the Late Heavy Bombardment some four billion years ago. The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a period of time approximately 3800 to 4100 million years ago ( mya ^[2]

The brightness and purity of the water ice in Saturn's rings has been cited as evidence that the rings are much younger than Saturn, perhaps 100 million years old, as the infall of meteoric dust would have led to darkening of the rings. However, new research indicates that the B Ring may be massive enough to have diluted infalling material and thus avoided substantial darkening over the age of the Solar system. Ring material may be recycled as clumps form within the rings and are then disrupted by impacts. This would explain the apparent youth of some of the material within the rings. ^[3]

The Cassini UVIS team, led by Larry Esposito, used stellar occultation to discover 13 objects, ranging from 27 meters to 10 km across, within the F ring. Larry W Esposito (born April 15, 1951) is an American planetary astronomer and a Professor at the Laboratory for Atmospheric and Space Physics In Shia Islam The Occultation is a term used to designate the hidden state of the Imam of the Time. Saturn has the most extensive Planetary ring system of any planet in the Solar System. They are translucent, suggesting they are temporary aggregates of ice boulders a few meters across. Esposito believes this to be the basic structure of the Saturnian rings, particles clumping together, then being blasted apart.

Subdivisions and structures within the rings

The densest parts of the Saturnian ring system are the A and B Rings, which are separated by the Cassini Division (discovered in 1675 by Giovanni Domenico Cassini). Giovanni Domenico Cassini ( June 8, 1625 &ndash September 14, 1712) was an Italian Mathematician, Astronomer Along with the C Ring, which was discovered in 1850 and is similar in character to the Cassini Division, these regions comprise the Main Rings. The Main Rings are denser and contain larger particles than the tenuous Dusty Rings. The latter include the D Ring, extending inward to Saturn's cloud tops, the G and E Rings and others beyond the main ring system. The word "dusty" used to characterize these diffuse rings refers to the small size of the particles (often about a micron); their chemical composition is, like the main rings, almost entirely of water ice. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia The narrow F Ring, just off the outer edge of the A Ring, is more difficult to categorize; parts of it are very dense, but it also contains a great deal of dust-size particles.

Natural-color mosaic of Cassini narrow-angle camera images of the unilluminated side of Saturn's D, C, B, A and F rings (left to right) taken on May 9, 2007. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Events 1457 BC - Battle of Megiddo (15th century BC between Thutmose III and a large Canaanite coalition under the King of Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.

The illuminated side of Saturn's rings with the major subdivisions labelled

Major subdivisions of the rings

Structures within the C Ring

Structures within the Cassini Division

Structures within the A Ring

Notes:
⁽¹⁾ distance is to centre of gaps, rings and ringlets that are narrower than 1000 km
⁽²⁾ unofficial name
⁽³⁾ Names as designated by the International Astronomical Union, unless otherwise noted. Giovanni Domenico Cassini ( June 8, 1625 &ndash September 14, 1712) was an Italian Mathematician, Astronomer Édouard Albert Roche (1820-1883 was a French scientist who is best known for his work in the field of Celestial mechanics. Saturn X redirects here For the spurious moon reported in 1905 see Themis (moon TemplateInfobox Planet.--> Epimetheus (ˌɛpɨˈmiːθiəs,, or Giuseppe Colombo ( October 2, 1920  – February 20, 1984) better known by his nickname Bepi Colombo, was an Italian Scientist TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as James Clerk Maxwell (13 June 1831 &ndash 5 November 1879 was a Scottish mathematician and theoretical physicist. Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch Johann Franz Encke ( 23 September 1791 – 26 August 1865) was a German Astronomer, born in Hamburg. James Edward Keeler ( September 10 1857 – August 12 1900) was an American Astronomer. Broader separations between named rings are termed divisions, while narrower separations within named rings are called gaps.
⁽⁴⁾ Data mostly from the Gazetteer of Planetary Nomenclature and this NASA factsheet.

Oblique (4 degree angle) Cassini images of Saturn's C, B, and A rings (left to right; the F ring is faintly visible in the full size upper image if viewed at sufficient brightness). Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Upper image: natural color mosaic of Cassini narrow-angle camera photos of the illuminated side of the rings taken on December 12, 2004. Events 627 - Battle of Nineveh: A Byzantine army under Emperor Heraclius defeats Emperor Khosrau II 's Persian "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Lower image: simulated view constructed from a radio occultation observation conducted on May 3, 2005. Radio occultation (RO is a Remote sensing technique used for measuring the physical properties of a planetary Atmosphere. Events 1491 - Kongo monarch Nkuwu Nzinga is baptised by Portuguese missionaries adopting the baptismal name of João Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Color in the lower image is used to represent information about ring particle sizes.

D Ring

A Cassini image of Saturn's D ring processed to show faint ripples within it; the much brighter C ring appears in the upper left.

The D Ring is the innermost ring, and is very faint. In 1980, Voyager 1 detected within this ring three ringlets designated D73, D72 and D68, with D68 being the discrete ringlet nearest to Saturn. The Voyager 1 spacecraft is a 722-kilogram robotic Space probe of the outer Solar system and beyond launched September 5, Some 25 years later Cassini images showed that D72 had become significantly fainter and moved planetward by 200 kilometres. Present in the gap between the C ring and D73 is finescale structure with waves 30 kilometres apart.

C Ring

The Maxwell Gap, with the Maxwell Ringlet on its right side, lies above and right of center in this Cassini image of Saturn's outer C Ring.

The C Ring is a wide but faint ring located inward of the B Ring. It was discovered in 1850 by William and George Bond, though William R. Dawes and Johann Galle also saw it independently. William Cranch Bond ( September 9, 1789 &ndash January 29, 1859) was an American Astronomer, and the first director of Harvard George Phillips Bond ( May 20, 1825 &ndash February 17, 1865) was an American Astronomer. William Rutter Dawes ( 19 March 1799 – 15 February 1868) was an English Astronomer. Johann Gottfried Galle ( June 9, 1812 &ndash July 10, 1910) was a German Astronomer at the Berlin Observatory William Lassell termed it the "Crepe Ring" because it seemed to be composed of darker material than the brighter A and B Rings. William Lassell ( June 18 1799 &ndash October 5 1880) was an English Astronomer. ^[4]

Its vertical thickness is estimated at 5 metres, its mass at around 1. 1×10¹⁸ kilograms, and its optical depth varies from 0. Optical depth is a measure of transparency, and is defined as the negative Logarithm of the fraction of Radiation (or Light) that is scattered 05 to 0. 12. [1]. That is, 5 and 12 percent of light shining through perpendicular to the ring is blocked, so that when seen from above or below, the ring is close to transparent.

Colombo Gap and Titan Ringlet

The Colombo Gap lies in the inner C Ring. Within the gap lies the bright but narrow Colombo Ringlet, centered at 77,883 kilometers from Saturn's center, which is slightly elliptical rather than circular. In Mathematics, an ellipse (from the Greek ἔλλειψις literally absence) is a Conic section, the locus of points in a This ringlet is also called the Titan Ringlet as it is governed by an orbital resonance with the moon Titan. In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as [2] At this location within the rings, the time period of a ring particle's apsidal precession is equal to the time period of Titan's orbital motion, so that the outer end of this eccentric ringlet always points towards Titan. Precession refers to a change in the direction of the axis of a rotating object

Maxwell Gap

The Maxwell Gap lies within the outer C Ring. It also contains a dense non-circular ringlet, the Maxwell Ringlet.

B Ring

Dark B ring spokes are visible in this Cassini image of the unilluminated side of the rings. Left of center, two dark gaps (the larger being the Huygens Gap) and the bright (from this viewing geometry) ringlets between and immediately beyond them comprise the Cassini Division.

The B Ring is the largest, brightest, and most massive of the rings. Its thickness is estimated as 5 to 10 metres, its mass at 2. 8×10¹⁹ kg, and its optical depth varies from 0. Optical depth is a measure of transparency, and is defined as the negative Logarithm of the fraction of Radiation (or Light) that is scattered 4 to 2. 5, [3] meaning that well over 99% of the light passing through some parts of the B Ring is blocked. The B Ring contains a great deal of variation in its density and brightness, nearly all of it unexplained. These are concentric, appearing in the form of narrow ringlets, though the B Ring does not contain any gaps. Concentric objects share the same center, axis or origin with one inside the other

Spokes

During the Voyager encounters, extended short-lived spoke-like features were seen in the B ring under some viewing geometries. See also Voyager 1 and Voyager 2. The Voyager program consists of a pair of unmanned scientific probes Voyager 1 and Their nature was the focus of lively scientific debate, and several hypotheses were proposed as to their cause and makeup. Spokes were seen by the Hubble Space Telescope in the late 1990s and early 2000s. The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into When the Cassini spacecraft entered into orbit around Saturn, the spokes were mysteriously absent. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Suggestions that spokes may be a seasonal effect, varying with Saturn's 29. A season is one of the major divisions of the Year, generally based on yearly periodic changes in Weather. 7-year orbit, were supported by their gradual reappearance in the later years of the Cassini mission. A year (from Old English gēr) is the time between two recurrences of an event related to the Orbit of the Earth around the Sun The leading theory is that spokes are made of tiny dust particles suspended above the main ring by electrostatic repulsion. Electrostatics is the branch of Science that deals with the Phenomena arising from what seems to be stationary Electric charges Since Classical Suggestions for the origin of the electrical disturbances include lighting bolts in Saturn's atmosphere and micrometeoroid impacts on the rings. A Micrometeoroid (also micrometeorite, micrometeor) is a tiny Meteoroid; a small particle of rock in space usually weighing less than a Gram The spokes appear dark in backscattered light, and bright in forward-scattered light. Backscatter is the reflection of Waves particles or signals back to the direction they came from In Telecommunication and Astronomy, forward scatter is the Deflection --by Diffraction, nonhomogeneous Refraction, or nonspecular

Cassini Division

The Cassini Division is a 4,800 km (2,980 mile) wide region between the A Ring and B Ring. It was discovered in 1675 by Giovanni Cassini. Giovanni Domenico Cassini ( June 8, 1625 &ndash September 14, 1712) was an Italian Mathematician, Astronomer From Earth it appears as a thin black gap in the rings. However, Voyager discovered that the gap is itself populated by ring material bearing much similarity to the C Ring. See also Voyager 1 and Voyager 2. The Voyager program consists of a pair of unmanned scientific probes Voyager 1 and The division may appear bright in views of the unlit side of the rings, since the relatively low density of material allows more light to be transmitted through the thickness of the rings.

The inner edge of the Cassini Division is governed by a strong orbital resonance. In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their Ring particles at this location orbit twice for every orbit of the moon Mimas. TemplateInfobox Planet. --> Mimas (ˈmaɪməs, or as Greek The resonance causes Mimas' pulls on these ring particles to accumulate, destabilizing their orbits and leading to a sharp cutoff in ring density. Many of the other gaps between ringlets within the Cassini Division, however, are unexplained.

Huygens Gap

The Huygens Gap is at the inner edge of the Cassini Division. It contains the dense Huygens Ringlet, which is non-circular.

A Ring

The A Ring is the outermost of the large, bright rings. Its inner boundary is the Cassini Division and its sharp outer boundary is close to the orbit of the small moon Atlas. TemplateInfobox Planet.--> Atlas (ˈætləs, or as Greek Άτλας The A Ring is interrupted at a location 22% of the ring width from its outer edge by the Encke Gap. A narrower gap 2% of the ring width from the outer edge is called the Keeler Gap.

The thickness of the A Ring is estimated as 10 to 30 metres, its mass as 6. 2×10¹⁸ kg (about the mass of Hyperion), and its optical depth varies from 0. TemplateInfobox Planet.--> Hyperion (haɪˈpɪəriən, or as in Optical depth is a measure of transparency, and is defined as the negative Logarithm of the fraction of Radiation (or Light) that is scattered 4 to 1. 0. [4]

Similarly to the B Ring, the A Ring's outer edge is maintained by an orbital resonance, in this case the 7:6 resonance with Janus and Epimetheus. In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their Saturn X redirects here For the spurious moon reported in 1905 see Themis (moon TemplateInfobox Planet.--> Epimetheus (ˌɛpɨˈmiːθiəs,, or Other orbital resonances also excite many spiral density waves in the A Ring (and, to a lesser extent, other rings as well), which account for most of its structure. Density wave theory or the Lin-Shu density wave theory is a theory proposed by C These waves are described by the same physics that describes the spiral arms of galaxies. A spiral galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Spiral bending waves, also present in the A Ring and also described by the same theory, are vertical corrugations in the ring rather than compression waves. A transverse wave is a moving Wave that consists of oscillations occurring perpendicular to the direction of energy transfer Longitudinal waves are waves that have vibrations along or parallel to their direction of travel that is waves in which the motion of the medium is in the same direction as the motion

Encke Gap

The Encke Gap is a 325-kilometre-wide gap within the A Ring, centered at a distance of 133,590 kilometers from Saturn's center. [5] It is caused by the presence of the small moon Pan, which orbits within it. For the moon of Jupiter known by this name 1955-1975 see Carme (moon. Images from the Cassini probe have shown that there are at least three thin, knotted ringlets within the gap. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its

Johann Encke himself did not observe this gap; it was named in honour of his ring observations. Johann Franz Encke ( 23 September 1791 – 26 August 1865) was a German Astronomer, born in Hamburg. The gap itself was discovered by James Edward Keeler in 1888. James Edward Keeler ( September 10 1857 – August 12 1900) was an American Astronomer.

The Encke Gap is a gap because it is entirely within the A Ring. There was some ambiguity between the terms gap and division until the IAU clarified the definitions in 2008; prior to that, the separation was sometimes called the "Encke Division".

Keeler Gap

The Keeler Gap is a 42-kilometre-wide gap in the A Ring, approximately 250 kilometres from the ring's outer edge. It is named after the astronomer James Edward Keeler. James Edward Keeler ( September 10 1857 – August 12 1900) was an American Astronomer. The small moon Daphnis, discovered May 1, 2005, orbits within it, keeping it clear. Daphnis (ˈdæfnɨs, or as Greek Δαφνίς is an Inner satellite of Saturn. Events 305 - Diocletian and Maximian retire from the office of Roman Emperor. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar.

The Encke Gap's central ringlet coincides with Pan’s orbit, implying its particles oscillate in horseshoe orbits. For the moon of Jupiter known by this name 1955-1975 see Carme (moon. A horseshoe Orbit appears when a viewer on an orbiting body (like Earth watches the movement of another orbiting body whose orbit is skinnier (more eccentric but has about Spiral density waves (induced by resonances with nearby moons), which pervade much of the A Ring, are visible on both sides of the gap. Density wave theory or the Lin-Shu density wave theory is a theory proposed by C In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their Saturn has 60 confirmed moons. These include 22 regular satellites, which all have Prograde orbits that are not greatly inclined with respect

The motion of Pan (not visible) through the Encke Gap induces edge waves and a set of spiraling wakes (which are not self-propagating) ahead of it in its orbit on the gap's inner side. For the moon of Jupiter known by this name 1955-1975 see Carme (moon. In Mathematics, a spiral is a Curve which emanates from a central point getting progressively farther away as it revolves around the point The other more tightly wound bands are spiral density waves. Density wave theory or the Lin-Shu density wave theory is a theory proposed by C

The passage of Daphnis induces waves in the edges of the Keeler gap. Daphnis (ˈdæfnɨs, or as Greek Δαφνίς is an Inner satellite of Saturn. Orbital motion is to the lower left; speed decreases going towards the A Ring edge.

Moonlets

In 2006, four tiny "moonlets" were found in Cassini images of the A Ring. ^[5] The moonlets themselves are only about a hundred meters in diameter, too small to be seen directly; what Cassini sees are the "propeller"-shaped disturbances the moonlets create, which are several km across. It is estimated that the A Ring contains thousands of such objects. In 2007, the discovery of eight more moonlets revealed that they are largely confined to a 3000-km belt, about 130,000 km from Saturn's center. ^[6] Over 150 "propeller" moonlets have now been detected. ^[7]

Location of the first four moonlets detected.

Roche Division

The separation between the A Ring and the F Ring has been named the Roche Division in honor of the French physicist Édouard Roche. Édouard Albert Roche (1820-1883 was a French scientist who is best known for his work in the field of Celestial mechanics. [6] The Roche Division should not be confused with the Roche limit, a physical concept that describes when a large object gets so close to a planet (such as Saturn) that the planet's tidal forces will pull it apart. Determining the Roche limit The Roche limit depends on the rigidity of the satellite The tidal force is a secondary effect of the Force of Gravity and is responsible for the Tides It arises because the gravitational acceleration experienced Lying at the outer edge of the main ring system, the Roche Division is in fact close to Saturn's Roche limit, which is why the rings have been unable to accrete into a moon. In Astrophysics, the term accretion is used for at least two distinct processes

Like the Cassini Division, the Roche Division is not empty but contains a sheet of material. The character of this material is similar to the tenuous and dusty D, E, and G Rings. Two locations in the Roche Division have a higher concentration of dust than the rest of the region. These were discovered by the Cassini probe imaging team and were given temporary designations: R/2004 S 1, which lies along the orbit of the moon Atlas; and R/2004 S 2, centered at 138,900 km from Saturn's center, inward of the orbit of Prometheus. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its In ancient times only the Sun and Moon, a few hundred Stars and the most easily visible Planets had names TemplateInfobox Planet.--> Atlas (ˈætləs, or as Greek Άτλας TemplateInfobox Planet.--> Prometheus (proʊˈmiːθiəs,, or

F Ring

The F Ring is the outermost discrete ring of Saturn and perhaps the most active ring in the Solar system, with features changing on a timescale of hours. ^[8] It is located 3000 km beyond the outer edge of the A Ring. ^[9] It was discovered in 1979 by the Pioneer 11 imaging team. Pioneer 11 was the second mission (after its sister probe Pioneer 10) to investigate Jupiter and the Outer solar system and the first to explore the planet ^[10] It is very thin, just a few hundred kilometers wide, and is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside it. A planetary ring is a ring of Cosmic dust and other small particles Orbiting around a Planet in a flat disc-shaped region TemplateInfobox Planet.--> Prometheus (proʊˈmiːθiəs,, or There is also an Asteroid called 55 Pandora.

A mosaic of 107 images covering 255° (about 70%) of the F Ring, as it would appear if straightened out. The radial width (top to bottom) is 1500 km.

Recent closeup images from the Cassini probe show that the F Ring consists of one core ring and a spiral strand around it. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its They also show that when Prometheus encounters the ring at its apoapsis, its gravitational attraction creates kinks and knots in the F Ring as the moon 'steals' material from it, leaving a dark channel in the inner part of the ring. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from Since Prometheus orbits Saturn more rapidly than the material in the F ring, each new channel is carved about 3. 2 degrees in front of the previous one.

The shepherd moons Pandora (left) and Prometheus orbit on either side of the F ring; Prometheus is followed by dark channels that it has carved into the inner strands of the ring.

Close-up view of Prometheus and the F Ring. A movie of Prometheus at its apoapsis drawing a streamer of material out of the ring, leaving a dark channel, may be viewed here or here. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from

Prometheus (at center) and Pandora are the inner and outer F Ring shepherds.

In 2008, further dynamism was detected, suggesting that small unseen moons orbiting within the F Ring are continually colliding due to perturbations from the shepherds. One of the small moons was tentatively identified as S/2004 S 6. ^[8]

Dynamism due to collisions within the F Ring.

Outer Rings

"Janus/Epimetheus" Ring

A faint dust ring is present around the region occupied by the orbits of Janus and Epimetheus, as revealed by images taken in forward-scattered light by the Cassini spacecraft in 2006. Saturn X redirects here For the spurious moon reported in 1905 see Themis (moon TemplateInfobox Planet.--> Epimetheus (ˌɛpɨˈmiːθiəs,, or Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its The ring has a radial extent of about 5,000 km ^[11]. Its source is particles blasted off the moons' surfaces by meteoroid impacts, which then form a diffuse ring around their orbital paths. ^[12]

G Ring

The G Ring is a very thin, faint ring about halfway between the F Ring and the beginning of the E Ring, with its inner edge about 15000 km inside the orbit of Mimas. TemplateInfobox Planet. --> Mimas (ˈmaɪməs, or as Greek It contains a single distinctly brighter "arc" near its inner edge (similar to the arcs in the rings of Neptune) that extends about one sixth of its circumference, which is held in place by a 7:6 orbital resonance with Mimas. Neptune has a faint dusty Planetary ring system, which was discovered in 1989 by Voyager 2 spacecraft In Celestial mechanics, an orbital resonance occurs when two Orbiting bodies exert a regular periodic gravitational influence on each other usually due to their ^[13] The arc is believed to be composed of icy particles up to a few meters in diameter, with the rest of the G Ring consisting of dust released by collisions within the arc. The radial width of the arc is about 250 km, compared to a width of 6000 km for the G Ring as a whole. ^[13] The arc is thought to be the remains of a small icy moonlet about a hundred meters in diameter that broke up relatively recently. Dust released from the larger chunks by micrometeoroid impacts drifts outward from the arc due to interaction with Saturn's magnetosphere (whose plasma corotates with Saturn's magnetic field, which rotates much more rapidly than the orbital motion of the G Ring). A Micrometeoroid (also micrometeorite, micrometeor) is a tiny Meteoroid; a small particle of rock in space usually weighing less than a Gram A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges These tiny particles are steadily eroded away by further impacts and dispersed by plasma drag. Over the course of thousands of years the ring will gradually lose mass and eventually disappear. ^[14]

"Pallene" Ring

A faint dust ring shares Pallene's orbit, as revealed by images taken in forward-scattered light by the Cassini spacecraft in 2006. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its ^[11] The ring has a radial extent of about 2,500 km. Its source is particles blasted off Pallene's surface by meteoroid impacts, which then form a diffuse ring around its orbital path. ^[12]

E Ring

The E Ring is the outermost ring, and is extremely wide, beginning at the orbit of Mimas and ending somewhere around the orbit of Rhea. TemplateInfobox Planet. --> Mimas (ˈmaɪməs, or as Greek TemplateInfobox Planet.--> Rhea (ˈriːə, or as in Greek It is a diffuse disk of icy or dusty material. Unlike the other rings, it is composed of microscopic rather than macroscopic particles. In 2006, cryovolcanism on the moon Enceladus was determined to be the source of the E Ring's material. A cryovolcano is literally an Icy Volcano. Cryovolcanoes form on Icy moons and possibly on other low- Temperature Astronomical objects TemplateInfobox Planet.--> This article is about the moon of

The outer rings seen back-illuminated by the Sun. The Sun (Sol is the Star at the center of the Solar System.

The backlit G Ring and its bright inner arc. This image is part of a movie sequence showing the arc's orbital motion that may be viewed here or here.

The backlit E ring, with Enceladus silhouetted against it at center. The moon's south polar jets erupt brightly below it, while tendrils of the E Ring wrap around it.

Possible ring system around Rhea

Main article: Rings of Rhea

Saturn's second largest moon Rhea may have a tenuous ring system of its own consisting of three narrow bands embedded in a disk of solid particles. The Saturnian moon Rhea may have a tenuous ring system consisting of three narrow relatively dense bands within a particulate disk TemplateInfobox Planet.--> Rhea (ˈriːə, or as in Greek ^[15][16] These rings have not been imaged, but their existence has been inferred from Cassini observations in November of 2005 of a depletion of energetic electrons in Saturn's magnetosphere near Rhea. A magnetosphere' is a highly magnetized region around and possessed by an Astronomical object. The Magnetospheric Imaging Instrument (MIMI) observed a gentle gradient punctuated by three sharp drops in plasma flow on each side of the moon in a nearly symmetric pattern. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its This could be explained if they were absorbed by solid material in the form of an equatorial disk containing denser rings or arcs, with particles perhaps several decimeters to approximately a meter in diameter. However, not all scientists are convinced that the observations were caused by a ring system.

References

External links

• Planetary Rings Node: Saturn's Ring System
• Saturn's Rings by NASA's Solar System Exploration

See also

• Édouard Roche - French astronomer who described how the breakup of a satellite could form the rings, when it comes within the Roche limit of a celestial body. Édouard Albert Roche (1820-1883 was a French scientist who is best known for his work in the field of Celestial mechanics. Determining the Roche limit The Roche limit depends on the rigidity of the satellite
• Galileo Galilei - the first person to observe Saturn's rings, in 1610
• Christian Huygens - the first person to propose that there was a ring surrounding Saturn, in 1655
• Giovanni Cassini - discovered the separation between the A and B rings, in 1675 - (Cassini Division)