Rings of Saturn

For the 2005 television series, see E-Ring.

The rings of Saturn are a series of planetary rings that orbit the planet Saturn. They consist largely of ice and dust.

Galileo Galilei was the first person to observe Saturn's ring in 1610, although with his weak telescope, he could barely resolve them, and thought they were two moons on either side of the planet. In 1655, Christian Huygens was the first person to propose that there was a ring surrounding Saturn.

There are several gaps between the rings, all of which are caused by the gravitational pull of one or more of [[Saturn's natural satellites|Saturn's moons]] affecting the orbits of the tiny particles which comprise the rings.

Saturn's ring plane.jpg|thumb|300px|right|Saturn's rings; the major rings are labelled]]

Table

The IAU has designated the following names for the rings of Saturn and the gaps between them. This NASA factsheet provided most of the distances and widths.

Encke]]

Name	Distance from Saturn's center (km)	Width (km)	Named after
D Ring	66,900 - 74,510	7,500
C Ring ⁽³⁾	74,658 - 92,000	17,500
Columbo Gap	77,800 ? ⁽²⁾	100	Charles-Augustin de Coulomb (?)
Maxwell Gap	87,491 ⁽²⁾	270	James Clerk Maxwell
B Ring	92,000 - 117,580	25,500
Cassini Division	117,580 - 122,170	4,700	Giovanni Cassini
Huygens Gap	117,680 ? ⁽²⁾	285-440	Christiaan Huygens
A Ring	122,170 - 136,775	14,600
Encke Division	133,589 ⁽²⁾	325	Johann
Keeler Gap	136,530 ⁽²⁾	35	James Keeler
R/2004 S 1⁽¹⁾	137,630 ⁽²⁾	?
R/2004 S 2⁽¹⁾	138,900 ⁽²⁾	?
F Ring	140,180 ⁽²⁾	30-500
G Ring	170,000 - 175,000	5,000
E Ring	181,000 - 483,000	302,000

Note:
⁽¹⁾ temporary designation
⁽²⁾ distance is to centre of gaps, rings and ringlets that are narrower than 1000 km
⁽³⁾ C separated from D by Guerin Division, an official IAU designation from 1998

D Ring

The D Ring is the innermost ring. It is located inward of the C Ring, and is very faint indeed. In 1980 Voyager 1 had detected within this ring three ringlets designated D73, D72 and D68, with D68 being the discrete ringlet nearest to Saturn. 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

Saturnian rings.jpg|thumb|right|In this image of Saturn's rings, the C Ring is the faint ring below the two brighter ones]] The C Ring is a wide but faint ring located inward of the B Ring, and was discovered in 1850 by William and George Bond when it was termed the 'Crepe Ring' because it seemed to be composed of darker material than the brighter A and B Rings.

Its thickness is estimated as 5 metres, its mass as 1.1e18 kilogram, and its optical depth varies from 0.05 to 0.12.^*

Columbo Gap

The Columbo Gap lies in the middle of the C Ring, and contains the bright and narrow Titan ringlet (also called Columbo ringlet) centred at 77,883 kilometres from Saturn's centre. The ringlet is so named as it is a resonance with Titan.^*

Maxwell Gap

The Maxwell Gap lies within the C Ring.

B Ring

Saturn (planet) large.jpg|thumb|right|In this image of Saturn, the B Ring is the inner of the two wide rings, the Cassini Division is the gap between the two widest rings, and the A Ring is the outer of the two wide rings]]

The B Ring is the innermost of the two largest, brightest rings. Unlike the [[#A Ring|A Ring]], it is made of innumerable ringlets, some of which have eccentric orbits. There are also spoke-like features running across it, which are made of suspended dust particles.

Its thickness is estimated as 5 to 10 metres, its mass as 2.8e19 kilogram (about three-quarters of Mimas), and its optical depth varies from 0.4 to 2.5.^*

Huygens Gap

The Huygens Gap separates the B Ring from the Cassini Division.

Cassini Division

The Cassini Division is a 4,800 km (2,980 mile) region between the A Ring and B Ring. It was discovered in 1675 by Giovanni Cassini. From Earth it appears as a thin black gap in the rings. However, during the Voyager flybys, it was discovered that the gap is full of tiny rings.

Saturn's moon Mimas is responsible for clearing material from the Cassini Division.

A Ring

The A Ring is the outermost of the two largest, brightest rings. Its inner boundary is the Cassini Division and its sharp outer boundary is the orbit of the small moon Atlas. The A Ring is divided in two near its outer edge by the Encke Division. A smaller, fainter division is called the Keeler Gap, and is kept clear by the moonlet Daphnis.

Its thickness is estimated as 10 to 30 metres, its mass as 6.2e18 kilogram (about the mass of Hyperion), and its optical depth varies from 0.4 to 1.0.^*

Encke Division

The Encke Division, also historically called the Encke Gap, is a perceived gap within the A Ring. Encke himself did not observe this division, which was named in honour of his ring observations.

The division is centered at a distance 133,580 kilometers from Saturn's center, and has a width of 325 kilometers.^* It is caused by the presence of the small moon Pan, which orbits within it.

Images from the Cassini probe have shown that there are at least two thin, knotted ringlets within the gap.^*

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. The small moon Daphnis, discovered May 1 2005, orbits within it, keeping it clear.

R/2004 S 1

R/2004 S 1, also known as S/2004 1R, is the temporary designation of a newly discovered ring that lies between the A Ring and the F Ring, in the orbit of the moon Atlas. The faint, thin ring was discovered by the Cassini probe imaging team and announced on September 9, 2004.

R/2004 S 2

R/2004 S 2 is a temporary designation for a faint ring recently discovered by the Cassini probe imaging team and announced in 2005. The ring is located at 138,900 km from Saturn's center, between the orbits of Atlas and Prometheus.

F Ring

The F Ring is one of the outer rings of Saturn. It is located outside the larger rings, just beyond about 3000 Km, the A Ring. It was discovery in 1979. It is very thin, just few hundred of kilometers wide, and is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside it.

Recent closeup images from the Cassini probe show that the F Ring consists of one core ring and a spiral strand around it ^*. They also show that Prometheus's gravitational attraction creates kinks and knots in the F Ring as the moon 'steals' material from it.

Image:F Ring.jpg|The F Ring is the thin ring on the right; its shepherd moons Prometheus and Pandora can be seen on either side of it. Image:Prometheus's effect on the F Ring.jpg|Close up view of Prometheus and the F Ring Image:Shepherd moons PIA07653.jpg|Prometheus (at left) and Pandora (at right) shepherding the F Ring

G Ring

G_ring.jpg|thumb|right|The G Ring is the faint, thin line to the left of this image; to the right are the F Ring, Encke Division and A Ring.]]

The G Ring is a very thin, faint ring about halfway between the F Ring and the beginning of the E Ring.

E Ring

For other meanings see E Ring (disambiguation).

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. 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, cryovulcanism on the moon Enceladus was determined to be the source of the E Ring's material.

References

External links

Saturn | Planetary rings

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