Rings of Saturn
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● D-ring (bluish, close to Saturn)
● C-, B- and A-rings (very clearly visible)
● F-ring (narrow, very bright ring)
● Janus / Epimetheus ring (narrow, pale)
● G ring
● Pallene ring (pale, easy to see above and below Saturn)
● E ring
The Rings of Saturn (or Saturn's Rings ) are a large number of essentially chunks of ice and rock that orbit Saturn . The particle size varies between that of dust particles and several meters. Viewed from a distance, they together form a ring system that surrounds the planet Saturn . The ring system has many larger and smaller gaps. It is the most noticeable feature of the planet and can be seen through a telescope from about 40x magnification . The two brightest rings (A and B rings) were therefore discovered with the advent of telescopes in 1610, and the almost transparent C or pile ring on the inside in 1850. The four other, very fine structures could only be discovered by three space probes between 1979 and in 1981.
With a thickness of between 10 and 100 meters and a diameter of almost a million kilometers, the rings are extremely thin. They lie exactly in the equatorial plane of Saturn and cast a visible shadow on it - as does Saturn on its rings, vice versa. The shadow cast on the surface of Saturn is more pronounced the more the thin ring system with its narrow "edge" is inclined towards the sun in the course of a Saturn year.
Discovery and naming
Saturn's rings are named according to the order in which they were discovered and, from the inside out, are called D, C, B, A, F, G, and E rings. The total mass of all Saturn's rings is 30 quadrillion tons, which corresponds roughly to the mass of an asteroid almost 300 kilometers in diameter. On astronomical overview recordings, usually only the A and B rings and the Cassini division separating them, or at most the Encke division in the A ring, can be seen. The latter was first observed on January 7, 1888 by James Edward Keeler at the Lick Observatory . It was only through space probes that it was recognized that the rings again had gaps and were divided into even smaller, narrowly defined sub-rings.
The ring system itself was discovered in July 1610 by Galileo Galilei with one of the first telescopes . However, Galileo did not recognize the rings as isolated objects, but interpreted them as handles ( ansae ). The Dutch astronomer Christiaan Huygens correctly described the rings 45 years later:
- "Saturn is surrounded by a thin, flat ring which does not touch it anywhere and which is inclined towards the ecliptic " .
Giovanni Domenico Cassini was the first to suspect that the rings consist of individual particles, and in 1675 discovered the most striking gap in the ring system, the Cassini division named after him, which divides the then known ring into a lighter outer A-ring and a slightly darker inner B- Ring shared.
The next weaker C-ring was discovered by George Phillips Bond on November 15, 1850.
The blue and even weaker inner D-ring was discovered in 1969 by Pierre Guérin ; a first suspicion, however, dates back to 1933 from NP Barabashov and B. Semejkin.
The E-ring (originally the exterior ring) was discovered in 1967 on recordings from the previous year by Walter Feibelman .
The F-ring was discovered by Pioneer 11 in September 1979.
The G-Ring was discovered by Voyager 1 in November 1980.
The Saturn orbiter Cassini discovered another faint dust ring on September 17, 2006. This ring is located outside the bright main rings between the faint rings F and G, in the area of the orbits of the small moons Janus and Epimetheus . He probably consists of particles of these satellites at impacts of meteorites were hurled into space.
With the Spitzer Space Telescope in 2009, a ring (better: a cloud of dust) lying much further out and independent of the main ring system was discovered by means of its infrared radiation. The ring cannot be seen visually due to its very low density of matter and the weak reflection of sunlight . The ring extends over a distance of 6 to 12 million kilometers from Saturn and is about 2.5 million kilometers thick. According to the JPL , which looks after the Spitzer space probe on behalf of NASA, the earth would find space in the ring about a billion times. If it were visible from Earth, it would appear twice the size of the full moon. It is inclined by 27 ° against the inner ring system. It is believed that the ring was made from material from the moon Phoebe . This rotates with the newly discovered ring system, compared to the previously known rings, in the opposite direction around Saturn.
In 2015, the WISE space telescope found that the ring extends at a distance of 6 to 16 million kilometers from the surface of Saturn. It consists mainly of very small, dark dust that is distributed extremely widely.
structure
For a long time there was speculation about the consistency and physical state of the rings. In 1856, James Clerk Maxwell showed that stable rings can only exist if they are made up of a multitude of disconnected small solid bodies.
Today it is known that the main ring system contains more than 100,000 individual rings with different compositions and colors, which are separated from each other by sharply defined gaps. The innermost already begins about 7000 km above the surface of Saturn and has a diameter of 134,000 km, the outermost has a diameter of 960,000 km.
The ring particles orbit Saturn rechtläufig in the equatorial plane ; thus the ring system as well as the equatorial plane is inclined by 27 ° to Saturn's orbital plane. Every 14.8 years, i.e. roughly every half a Saturn year, the earth passes the ring plane, so that the ring system becomes almost invisible. In September 2009 the earth changed from the southern to the northern hemisphere of Saturn.
Another phenomenon are radial , spoke-like structures that extend from the inside out over the rings of Saturn and take on enormous dimensions: at a width of around 100 km, they can be up to 20,000 km long. These spokes were first discovered by the Voyager 2 probe during its passage in 1981. a. confirmed by the Hubble Space Telescope . Oddly enough, however, these structures gradually disappeared from 1998 and could not be detected again until September 2005 on images taken by the Cassini space probe . A short-lived interaction with the magnetic field of Saturn was initially assumed to be the cause of the banding .
In 2006, however, American astronomers found another explanation for the puzzle about the spoke structures: According to this, the spokes consist of tiny (a few µm ) charged dust particles whose trajectory is influenced by the sun's UV light in such a way that the particles move into place through the resulting electrostatic forces be brought into a state of suspension ( levitation ) and lifted. Depending on the position of Saturn on its orbit , the angle between Saturn's rings and the sun changes and thus also the angle of incidence of the ultraviolet light. The dark stripes appear at periodic intervals whenever the sun is in the ring plane of Saturn and then exist for about 8 years. A streak-free phase, on the other hand, lasts for 6 to 7 years. The reason for the electrostatic charging of the rings is controversial. One explanation is that lightning bolts occur in the upper atmosphere of Saturn, which through complex processes create electron beams that hit the rings.
dynamics
The gaps between the rings are based on the gravitational interaction with the numerous moons of Saturn and the rings with one another. Resonance phenomena also play a role here, which occur when the cycle times are in the ratio of small whole numbers. Thus the Cassini division is caused by the moon Mimas . Some smaller moons, so-called shepherd or shepherd moons , circle directly in the gaps and at the edges of the ring system and stabilize its structure. New measurements and recordings from the Cassini space probe have shown that the edges of the rings and thus the separation of the rings are even sharper than previously assumed. It was suspected that there were also some chunks of ice in the gaps, but this is not the case.
The extremely small thickness of the ring system is due to the impact of the particles. Each lump orbits individually around the center of Saturn and not the rings as a rigid structure. Therefore, every lump that is at some point on the surface of the ring system oscillates vertically through the ring system and back again during one revolution. By inelastic collisions with other chunks of this vertical velocity component and thus the thickness of the ring system is reduced.
Emergence
There are various theories about the origin of Saturn's rings . According to the theory proposed by Édouard Albert Roche as early as the 19th century , the rings were created by a moon that has come so close to Saturn that it broke apart due to tidal forces . The critical distance is called the Roche limit . In this case, the spatial variation of the gravitational forces caused by Saturn exceeds the moon's internal gravitational forces , so that the moon is only held together by its material structure. After a modification of this theory, the moon was broken by a collision with a comet or asteroid . According to another theory, the rings were created from the same cloud of matter together with Saturn itself. This theory was hardly supported until recently, because it was assumed that the rings represent a rather short-lived phenomenon by astronomical standards of at most a few hundred million years.
Radii and orbital times of the rings of Saturn and the moons involved
Structure of the D-ring and the beginning C-ring (lower area of the picture), the Colombo division can be seen in the lower corners (Cassini, 2015, strongly lightened)
Saturn and rings with mutual shadows (Cassini, 2004)
Saturn's rings: the main rings A to D and F are marked (Cassini-Huygens, 2004)
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| object | Orbit radius (size) (km) |
Orbital time | image |
|---|---|---|---|
| Saturn surface | 60,250 | 10.55 h |
 |
| D-ring and beginning C-ring (right quarter) of Saturn (100 km ~ 16.5 pixels) |
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| D-ring (inside) | 66,900 | 4.90 h |
 |
| D-ring (outside) | 74,510 | 5.76 h |
 |
| C-ring of Saturn (100 km ~ 16.5 pixels) |
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| C-ring (inside) | 74,658 | 5.78 h |
 |
| Colombo division | 77,870 (150) | 6.16 h |
 |
| Titanium ring bow | 77,870 (25) | 6.16 h | |
| Maxwell division | 87,491 (270) | 7.33 h |
 |
| Maxwell ring arch | 87,491 (64) | 7.33 h | |
| Bond division | 88,700 (30) | 7.49 h |
 |
| 1.470R S ring arch | 88,716 (16) | 7.49 h | |
| 1.495R S ring arch | 90,171 (62) | 7.67 h |
 |
| Dawes division | 90,210 (20) | 7.68 h | |
| C-ring (outside) | 92,000 | 7.91 h |
 |
| B-ring of Saturn (100 km ~ 16 pixels) |
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| B-ring (inside) | 92,000 | 7.91 h |
 |
| ? S / 2009 S 1 (0.3) | 117,100 | 11.36 h |
 |
| B-ring (outside) | 117,580 | 11.43 h |
 |
| Cassini division of Saturn (100 km ~ 16 pixels) |
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| Cassinian division (inside) | 117,580 | 11.43 h |
 |
| Huygens division | 117,680 (285-400) | 11.44 h | |
| Huygens ring arch | 117,848 (17) | 11.47 h | |
| Herschel division | 118,234 (102) | 11.52 h |
 |
| Russell division | 118,614 (33) | 11.58 h |
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| Jeffreys division | 118,950 (38) | 11.63 h |
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| Kuiper division | 119,405 (3) | 11.69 h |
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| Laplace division | 119,967 (238) | 11.78 h |
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| Bessel division | 120,241 (10) | 11.82 h |
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| Barnard division | 120,312 (13) | 11.83 h | |
| Cassinian division (outside) | 122,170 | 12.10 h |
 |
| A-ring of Saturn (100 km ~ 15 pixels) |
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| A-ring (inside) | 122,170 | 12.10 h |
 |
| Encke division | 133,589 (325) | 13.84 h |
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| ? Pan (28) | 133,584 | 13.84 h |
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| ? Daphnis (8) | 136,500 | 14.29 h |
.jpg){kind=small} |
| Keeler division | 136,505 (35) | 14.29 h |
 |
| A-ring (outside) | 136,775 | 14.34 h | |
| Roche division of Saturn (100 km ~ 16 pixels) |
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| Roche division (inside) | 136,775 | 14.34 h |
 |
| ? Atlas (31) | 137,700 | 14.48 h |
 |
| Roche division (outside) | 139,380 | 14.75 h |
 |
| F-ring of Saturn (100 km ~ 17 pixels) |
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| ? Prometheus (86) | 139,400 | 14.75 h |
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| F-ring (inside) | 140.180 | 14.87 h |
 |
| F-ring (outside) | 140.180 | 14.87 h | |
| ? Pandora (81) | 141,700 | 15.12 h |
 |
| Janus / Ephimetheus-Ring (inner half, 100 km ~ 17 pixels) |
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| Janus / Epimetheus ring (inside) | 149,000 | 16.30 h |
 |
| ? Epimetheus (113) | 151.410 | 16.6640 h |
 |
| ? Janus (178) |
 |
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| Janus / Epimetheus ring (outside) | 154,000 | 17.13 h |
|
| G-ring |
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| G-ring (inside) | 166,000 | 19.17 h |
|
| ? Aegaeon (0.6) | 167,500 | 19.43 h |
 |
| G-ring (outside) | 175,000 | 20.75 h |
|
| E ring |
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| E-ring (inside) | 180,000 | 21.64 h |
 |
| ? Mimas (397) | 185,600 | 22.66 h |
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| ? Methone (3) | 194,000 | 24.22 h |
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| Methone ring arch | 194.230 | 24.26 h |
 |
| Anthe ring arch | 197,665 | 24.91 h |
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| ? Anthe (2) | 197,700 | 24.91 h |
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| Pallene ring (inside) | 211,000 | 27.5 h |
|
| ? Pallene (5) | 212.280 | 27.7193 h |
 |
| Pallene ring (outside) | 213,500 | 28.0 h |
|
| ? Enceladus (504) | 238.040 | 32.8852 h |
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| ? Tethys (1062) | 294,619 | 45.3072 h |
 |
| ? Telesto (25) |
 |
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| ? Calypso (21) |
 |
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| ? Dione (1123) | 377.420 | 65.688 h |
 |
| ? Helene (35) |
 |
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| ? Polydeuces (2.5) |
 |
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| E-ring (outside) | 480,000 | 94 h |
|
| ? Rhea (1529) | 527.040 | 108.4386 h |
 |
| Phoebe ring (1 million km ~ 20 pixels) |
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| ? Iapetus (1436) | 3.5608 million | 79.33 d |
 |
| Phoebe ring (inside) | 4 million | 95 d |
 |
| ? Phoebe (213) | 12.952 million | 550.479 d |
 |
| Phoebe ring (outside) | 13 million | 550 d |
|
Other ring and disk phenomena in astronomy
Significantly weaker rings are also found in Jupiter , Uranus and Neptune , the other large gas planets in the solar system . In addition, circular discs in astronomy a common phenomenon in very different orders of magnitude occurs. In addition to planetary rings, these include accretion disks in X-ray binary stars and those that form in the formation phase of stars , such as the asteroid belt , but also the spiral galaxies . Here, too, the thickness of these panes is determined by the frequency of inelastic collisions between their components.
See also
Web links
- Current images of the Saturn rings by the Cassini probe on the FU Berlin website
- Overview of facts about the Saturn rings on NASA's website (English)
- Saturn, Titan, Rings and Haze on starobserver.org, Astronomy Picture of the Day July 29, 2013
- Collection of images of Saturn's rings and moons on intergalacticsafari.com
- Spektrum .de: Hardly any ring particles in the immediate vicinity of Saturn
Individual evidence
- ↑ Ring-a-Round the Saturn on nasa.gov, accessed May 27, 2017
- ↑ Dorling Kindersley Verlag GmbH: The Planets A visual journey through our solar system . Dorling Kindersley, Munich 2015, ISBN 978-3-8310-2830-6 , pp. 117 .
- ^ Discovery of the inner dark ring of Saturn. In: Monthly Notices of the Royal Astronomical Society. Volume 11, p. 20, bibcode : 1850MNRAS..11 ... 20B .
- ↑ Ron Baalke: Historical Background of Saturn's Rings , on solarviews.com, accessed May 27, 2017
- ↑ International Astronomical Union, Symposium No. 65, Exploration of the Planetary System, edited by A. Woszczyk, C. Iwaniszewska
- ↑ MS Bobrov: A study of the outermost ring of Saturn on cambridge.org, accessed on May 27, 2017
- ↑ Cassini discovers new Saturn ring ( Memento from September 30, 2007 in the Internet Archive ) - report at astronomie.de (Source: JPL / NASA ( Memento from December 10, 2007 in the Internet Archive ))
- ↑ The King of Rings. NASA, October 7, 2009, accessed October 7, 2009 .
- ↑ Nasa telescope discovers huge ring of Saturn. Der Spiegel, October 7, 2009, accessed October 7, 2009 .
- ↑ Saturn giant ring is even bigger , in scinexx.de, accessed: June 15, 2016 , the article states as the source: P. Hamilton, Michael F. Skrutskie, Anne J. Verbiscer, Frank J. Masci: Small particles dominate Saturn's Phoebe ring to surprisingly large distances , in Nature 522, 185-187 (June 11, 2015)
- ↑ James Clerk Maxwell: On the stability of the motions of Saturn's rings. Cambridge 1859 online .
- ↑ Ilka Lehnen-Beyel: Striped like lightning. Retrieved September 2, 2019 . , Image from science about the mysterious spokes in the ring system on Wissenschaft.de, November 28, 2006
- ^ CJ Mitchell et al.: Saturn's Spokes: Lost and Found. Science , March 17, 2006, Vol. 311. No. 5767, pp. 1587-1589
- ↑ Puzzling streaks: lightning is supposed to disturb Saturn's rings. In: Spiegel Online . November 27, 2006, accessed February 27, 2015 .