Ringe des Saturn

Saturn und seine Ringe (Voyager 2, 1981)
Saturn und seine Ringe gegen die Sonne aufgenommen (Cassini, 2006)
  ● D-Ring (bläulich, nahe Saturn)
  ● C-, B- und A-Ring (sehr gut sichtbar)
  ● F-Ring (schmaler, sehr heller Ring)
  ● Janus/Epimetheus-Ring (schmal, blass)
  ● G-Ring
  ● Pallene-Ring (blass, gut zu sehen ober- und unterhalb von Saturn)
  ● E-Ring

Als Ringe des Saturn (oder Saturnringe) wird das Ringsystem bezeichnet, das den Planeten Saturn umgibt. Es ist das auffälligste und charakteristische Merkmal des Planeten und durch ein Fernrohr ab etwa 40-facher Vergrößerung sichtbar. Die Ringe bestehen aus einer ungeheuren Anzahl einzelner kleiner Materialbrocken, die den Saturn umkreisen. Die Größe dieser Partikel, die im Wesentlichen aus Eis und Gestein bestehen, reicht von Staubteilchen bis zu einigen Metern. Aus der Ferne betrachtet erscheinen sie als geschlossener ringscheibenförmiger Körper.

Das Ringsystem wird von größeren und kleineren Lücken in konzentrische Einzelringe unterteilt. Die zwei hellsten Ringe (A- und B-Ring) wurden bereits mit den ersten Teleskopen im Jahr 1610 entdeckt, der innen anschließende, fast durchsichtige C- oder Florring erst 1850. Die vier weiteren, sehr feinen und lichtschwachen Gebilde wurden erst durch drei Raumsonden zwischen 1979 und 1981 nachgewiesen.

Die Ringe sind mit einer Dicke zwischen 10 und 100 Metern[1] bei einem Durchmesser von fast einer Million Kilometern extrem dünn. Sie liegen genau in der Äquatorebene des Saturn und werfen einen sichtbaren Schatten auf ihn – wie auch umgekehrt der Saturn auf seine Ringe. Der Schattenwurf auf die Saturnoberfläche ist umso ausgeprägter, je mehr das dünne Ringsystem im Laufe eines Saturnjahres mit seiner schmalen „Kante“ gegenüber der Sonne geneigt ist.

Entdeckung und Benennung

Phoebe-Ring (Künstlerische Darstellung)

Saturns Ringe sind entsprechend der Reihenfolge ihrer Entdeckung benannt und werden von innen nach außen als D-, C-, B-, A-, F-, G- und E-Ring bezeichnet. Insgesamt beträgt die Gesamtmasse aller Saturnringe 30 Billiarden Tonnen,[2] das entspricht etwa der Masse eines Asteroiden von knapp 300 Kilometer Durchmesser. Auf astronomischen Übersichtsaufnahmen sind gewöhnlich nur der A- und der B-Ring und die sie trennende Cassini-Teilung, allenfalls noch die Encke-Teilung im A-Ring zu sehen. Letztere wurde erstmals am 7. Januar 1888 von James Edward Keeler am Lick-Observatorium beobachtet. Erst durch Raumsonden erkannte man, dass die Ringe wiederum Lücken aufweisen und sich in noch kleinere eng begrenzte Unterringe aufteilen.

Das Ringsystem an sich wurde im Juli 1610 von Galileo Galilei mit einem der ersten Teleskope entdeckt. Galilei erkannte die Ringe jedoch nicht als isolierte Objekte, sondern deutete sie als Henkel (ansae). Der holländische Astronom Christiaan Huygens beschrieb die Ringe 45 Jahre später korrekt:

„Der Saturn ist von einem dünnen, flachen Ring umgeben, der ihn nirgends berührt und der zur Ekliptik geneigt ist“.

Giovanni Domenico Cassini vermutete als erster, dass die Ringe aus einzelnen Partikeln bestehen, und entdeckte 1675 die markanteste Lücke im Ringsystem, die nach ihm benannte Cassinische Teilung, die den damalig bekannten Ring in einen helleren äußeren A-Ring und einen etwas dunkleren inneren B-Ring teilte.

Der nächstschwächere C-Ring wurde von George Phillips Bond am 15. November 1850 entdeckt.[3][4]

Der blaue und noch schwächere innere D-Ring wurde 1969 von Pierre Guérin entdeckt; ein erster Verdacht stammt allerdings schon aus dem Jahr 1933 von N. P. Barabashov und B. Semejkin.[5][6]

Der E-Ring (ursprünglich Exterior-Ring) wurde 1967 auf Aufnahmen aus dem Vorjahr durch Walter Feibelman entdeckt.

Der F-Ring wurde im September 1979 durch Pioneer 11 entdeckt.

Der G-Ring wurde im November 1980 durch Voyager 1 entdeckt.

Der Saturn-Orbiter Cassini hat am 17. September 2006 einen weiteren, schwachen Staubring entdeckt. Dieser Ring befindet sich außerhalb der hellen Hauptringe zwischen den schwachen Ringen F und G, im Bereich der Umlaufbahnen der kleinen Monde Janus und Epimetheus. Er besteht vermutlich aus Teilchen, die von diesen Satelliten aus bei Einschlägen von Meteoriten ins All geschleudert wurden.[7]

Mit dem Spitzer-Weltraumteleskop wurde im Jahre 2009 ein wesentlich weiter außen liegender, vom Hauptringsystem unabhängiger Ring (besser Staubwolke) anhand seiner Infrarotstrahlung entdeckt. Visuell ist der Ring auf Grund seiner sehr geringen Materiedichte und der schwachen Reflexion des Sonnenlichts nicht zu erkennen. Der Ring erstreckt sich über einen Saturnabstand von 6 bis 12 Millionen Kilometer und ist etwa 2,5 Millionen Kilometer dick.[8] Nach Angaben des JPL, das im Auftrag der NASA die Raumsonde Spitzer betreut, fände die Erde etwa eine Milliarde Mal Platz in dem Ring. Wäre er von der Erde aus sichtbar, würde er doppelt so groß wie der Vollmond erscheinen. Gegen das innere Ringsystem ist er um 27° geneigt. Es wird angenommen, dass der Ring aus Material des Mondes Phoebe stammt. Dieser dreht sich mit dem neu entdeckten Ringsystem, im Vergleich zu den bisher bekannten Ringen, in die entgegengesetzte Richtung um den Saturn.[9]

Mit dem Weltraumteleskop WISE wurde 2015 festgestellt, dass sich der Ring in einer Entfernung von 6 bis 16 Millionen Kilometer von der Saturnoberfläche erstreckt. Er besteht hauptsächlich aus sehr kleinem, dunklen Staub, der extrem weiträumig verteilt ist.[10]

Struktur

Speichenartige Strukturen (Voyager 2, 1981)
Änderung der Perspektive des Saturns mit seinen Ringen über das Saturnjahr (von der Erde aus gesehen)

Lange Zeit wurde über die Konsistenz und den Aggregatzustand der Ringe spekuliert. Im Jahre 1856 zeigte James Clerk Maxwell, dass stabile Ringe nur existieren können, wenn sie aus einer Vielzahl nicht zusammenhängender kleiner fester Körper bestehen.[11]

Heute ist bekannt, dass das Hauptringsystem mehr als 100.000 einzelne Ringe mit unterschiedlichen Zusammensetzungen und Farbtönen beinhaltet, welche durch scharf umrissene Lücken voneinander abgegrenzt sind. Der innerste beginnt bereits etwa 7000 km über der Oberfläche des Saturn und hat einen Durchmesser von 134.000 km, der äußerste hat einen Durchmesser von 960.000 km.

Die Ringteilchen umkreisen den Saturn rechtläufig in dessen Äquatorebene; somit ist das Ringsystem ebenso wie die Äquatorebene um 26,73° gegen Saturns Bahnebene geneigt. Ungefähr jedes halbe Saturnjahr – genauer: abwechselnd jeweils nach 13,75 und 15,75 Jahren – passiert die Erde die Ringebene, so dass das Ringsystem nahezu unsichtbar wird. Die unterschiedlichen Zeiten beruhen darauf, dass der Saturn auf seiner elliptischen Bahn unterschiedlich schnell läuft, im Perihel mit 10,2 km/s und im Aphel mit 9,1 km/s. Am 10. August 2009 hat die Sonne von der südlichen in die nördliche Hemisphäre des Saturn gewechselt, am 6. Mai 2025 (nach 15,75 Jahren) wird sie dies in die umgekehrte Richtung tun. Die entsprechenden Daten für die Erde sind der 4. September 2009 bzw. der 23. März 2025. Zu diesen Zeiten ist der Ring, wenn überhaupt, dann nur als dünner Strich im Teleskop erkennbar.[12]

Ein weiteres Phänomen sind radiale, speichenartige Strukturen, die sich von innen nach außen über die Ringe des Saturn erstrecken und hierbei enorme Ausmaße annehmen: bei einer Breite von rund 100 km können sie bis zu 20.000 km lang werden.[13] Diese Speichen wurden erstmals von der Sonde Voyager 2 bei ihrer Passage im Jahr 1981 entdeckt, später konnte die Beobachtung u. a. vom Weltraumteleskop Hubble bestätigt werden. Rätselhafterweise verschwanden diese Strukturen aber ab 1998 allmählich und konnten dann erst wieder ab September 2005 auf Aufnahmen der Raumsonde Cassini nachgewiesen werden. Als Ursache für die Streifenbildung wurde zunächst eine kurzlebige Wechselwirkung mit dem Magnetfeld des Saturn vermutet.

US-amerikanische Astronomen fanden 2006 jedoch eine andere Erklärung für das Rätsel um die Speichenstrukturen: Demnach bestehen die Speichen aus winzigen (wenige µm) geladenen Staubpartikeln, deren Flugbahn vom UV-Licht der Sonne so beeinflusst wird, dass die Partikel durch entstehende elektrostatische Kräfte in einen Schwebezustand (Levitation) gebracht und angehoben werden[14]. Je nach Position des Saturn auf seiner Umlaufbahn ändert sich der Winkel zwischen den Saturnringen und der Sonne und somit auch der Einfallswinkel des ultravioletten Lichts. Die dunklen Streifen entstehen in periodischen Abständen immer dann, wenn die Sonne in der Ringebene des Saturn steht und bestehen dann für etwa 8 Jahre. Eine streifenlose Phase hält dagegen 6 bis 7 Jahre lang an. Der Grund für die elektrostatische Aufladung der Ringe wird kontrovers diskutiert. Eine Erklärung ist, dass Blitze in der oberen Atmosphäre des Saturn auftreten, welche durch komplexe Vorgänge Elektronenstrahlen erzeugen, die die Ringe treffen[15].

Hirtenmond Prometheus stabilisiert den F-Ring (Cassini, 29. Oktober 2004)

Dynamik

Die Lücken zwischen den Ringen beruhen auf der gravitativen Wechselwirkung mit den zahlreichen Monden des Saturn sowie der Ringe untereinander. Dabei spielen auch Resonanzphänomene eine Rolle, die auftreten, wenn die Umlaufszeiten im Verhältnis kleiner ganzer Zahlen stehen. So wird die Cassinische Teilung durch den Mond Mimas verursacht. Einige kleinere Monde, so genannte Hirten- oder auch Schäfermonde, kreisen direkt in den Lücken und an den Rändern des Ringsystems und stabilisieren dessen Struktur. Neue Messungen und Aufnahmen der Raumsonde Cassini haben ergeben, dass die Ringkanten und damit die Abtrennung der Ringe noch schärfer sind als bisher angenommen. So hatte man vermutet, dass sich in den Lücken ebenfalls einige Eisbrocken befinden, was aber nicht der Fall ist.

Aufnahmen des Propellers Santos Dumont

Größere Ringkörper, sogenannte Moonlets (engl., Möndchen), können durch gravitative Wechselwirkung in ihrer Umgebung langgezogene Strukturen erzeugen, die in der Fachliteratur als Propeller bezeichnet werden. Durch die unterschiedlichen Relativgeschwindigkeiten überholen weiter außerhalb kreisende Partikel das Moonlet, Teilchen innerhalb seiner Bahn kommen ihm entgegen. Die Ringmaterie wird also durch den größeren Körper in unterschiedliche Richtungen gravitativ gestreut und es entsteht die bezeichnende Gestalt. Während der Cassini-Mission konnten zahlreiche solcher Strukturen beobachtet werden, während die zugehörigen Moonlets zum Teil jenseits des optischen Auflösungsvermögens der Instrumente lagen. Prominente Moonlets, bzw. die zugehörigen Propeller werden in der Fachliteratur mit den Namen von Luftfahrtpionieren bezeichnet, so beispielsweise Earhart (nach Amelia Earhart) oder Santos-Dumont (nach Alberto Santos Dumont).[16]

Die extrem geringe Dicke des Ringsystems geht auf Stöße der Partikel zurück. Jeder Brocken kreist einzeln um den Mittelpunkt des Saturn und nicht die Ringe als starres Gebilde. Daher pendelt jeder Brocken, der sich irgendwann an der Oberfläche des Ringsystems befindet, während eines Umlaufs einmal vertikal durch das Ringsystem hindurch und wieder zurück. Durch inelastische Stöße mit anderen Brocken reduziert sich diese vertikale Geschwindigkeitskomponente und damit auch die Dicke des Ringsystems.

Entstehung

Zur Entstehung der Saturnringe gibt es verschiedene Theorien. Nach der von Édouard Albert Roche bereits im 19. Jahrhundert vorgeschlagenen Theorie entstanden die Ringe durch einen Mond, der sich dem Saturn so weit genähert hat, dass er durch Gezeitenkräfte auseinandergebrochen ist. Der kritische Abstand wird als Roche-Grenze bezeichnet. Die räumliche Variation der Anziehungskräfte durch den Saturn übersteigt in diesem Fall die mondinternen Gravitationskräfte, so dass der Mond nur noch durch seine materielle Struktur zusammengehalten wird. Nach einer Abwandlung dieser Theorie zerbrach der Mond durch eine Kollision mit einem Kometen oder Asteroiden. Nach einer anderen Theorie sind die Ringe gemeinsam mit dem Saturn selbst aus derselben Materiewolke entstanden. Diese Theorie wurde bis kürzlich kaum mehr vertreten, denn man vermutete, dass die Ringe ein nach astronomischen Maßstäben eher kurzlebiges Phänomen von höchstens einigen hundert Millionen Jahren darstellen.

Radien und Umlaufzeiten der Saturnringe und beteiligter Monde

Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
ObjektBahnradius
(Größe)    (km)
Umlaufzeit     Bild     
Saturnoberfläche060.250010,55 h
Saturn-Oberfläche
Saturn-Oberfläche
 
 D-Ring und beginnender C-Ring (rechtes Viertel) des Saturn  (100 km ~ 16,5 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
D-Ring (innen)066.900004,90 h
Innerer Teil des D-Ringes
Innerer Teil des D-Ringes
D-Ring (außen)074.510005,76 h
Äußerer Teil des D-Ringes
Äußerer Teil des D-Ringes
 
 C-Ring des Saturn  (100 km ~ 16,5 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
C-Ring (innen)074.658005,78 h
Innerer Teil des C-Ringes
Innerer Teil des C-Ringes
Colombo-Teilung077.870 0(150)006,16 h
Colombo-Teilung und Titan-Ringbogen
Colombo-Teilung und Titan-Ringbogen
Titan-Ringbogen077.870 00(25)006,16 h
Maxwell-Teilung087.491 0(270)007,33 h
Maxwell-Teilung und -Ringbogen
Maxwell-Teilung und -Ringbogen
Maxwell-Ringbogen087.491 00(64)007,33 h
Bond-Teilung088.700 00(30)007,49 h
Bond-Teilung und 1.470RS-Ringbogen
Bond-Teilung und 1.470RS-Ringbogen
1.470RS-Ringbogen088.716 00(16)007,49 h
1.495RS-Ringbogen090.171 00(62)007,67 h
1.495RS-Ringbogen und Dawes-Teilung
1.495RS-Ringbogen und Dawes-Teilung
Dawes-Teilung090.210 00(20)007,68 h
C-Ring (außen)092.000007,91 h
Äußerer Teil des C-Ringes
Äußerer Teil des C-Ringes
 
 B-Ring des Saturn  (100 km ~ 16 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
B-Ring (innen)092.000007,91 h
Innerer Teil des B-Ringes
Innerer Teil des B-Ringes
🌑 S/2009 S 1 (0,3)117.100011,36 h
S/2009 S 1
S/2009 S 1
B-Ring (außen)117.580011,43 h
Äußerer Teil des B-Ringes
Äußerer Teil des B-Ringes
 
 Cassinische Teilung des Saturn  (100 km ~ 16 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
Cassinische Teilung (innen)117.580011,43 h
Innerer Teil der Cassinische Teilung/Huygens-Teilung/Huygens-Ringbogen
Innerer Teil der Cassinische Teilung/Huygens-Teilung/Huygens-Ringbogen
Huygens-Teilung117.680 0(285-400)011,44 h
Huygens-Ringbogen117.848 00(17)011,47 h
Herschel-Teilung118.234 0(102)011,52 h
Herschel-Teilung
Herschel-Teilung
Russell-Teilung118.614 00(33)011,58 h
Russell-Teilung
Russell-Teilung
Jeffreys-Teilung118.950 00(38)011,63 h
Jeffreys-Teilung
Jeffreys-Teilung
Kuiper-Teilung119.405 000(3)011,69 h
Kuiper-Teilung
Kuiper-Teilung
Laplace-Teilung119.967 0(238)011,78 h
Laplace-Teilung
Laplace-Teilung
Bessel-Teilung120.241 00(10)011,82 h
Bessel- und Bernard-Teilung
Bessel- und Bernard-Teilung
Barnard-Teilung120.312 00(13)011,83 h
Cassinische Teilung (außen)122.170012,10 h
Äußerer Teil der Cassinischen Teilung
Äußerer Teil der Cassinischen Teilung
 
 A-Ring des Saturn  (100 km ~ 15 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
A-Ring (innen)122.170012,10 h
Innerer Teil des A-Ringes
Innerer Teil des A-Ringes
Encke-Teilung133.589 0(325)013,84 h
Encke-Teilung
Encke-Teilung
🌑 Pan (28)133.584013,84 h
Pan
Pan
🌑 Daphnis (8)136.500014,29 h
Daphnis
Daphnis
Keeler-Teilung136.505 00(35)014,29 h
Keeler-Teilung und äußerer Teil des A-Ringes
Keeler-Teilung und äußerer Teil des A-Ringes
A-Ring (außen)136.775014,34 h
 
 Roche-Teilung des Saturn  (100 km ~ 16 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
Roche-Teilung (innen)136.775014,34 h
Innerer Teil der Roche-Teilung
Innerer Teil der Roche-Teilung
🌑 Atlas (31)137.700014,48 h
Atlas
Atlas
Roche-Teilung (außen)139.380014,75 h
Äußerer Teil der Roche-Teilung
Äußerer Teil der Roche-Teilung
 
 F-Ring des Saturn  (100 km ~ 17 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
🌑 Prometheus (86)139.400014,75 h
Prometheus
Prometheus
F-Ring (innen)140.180014,87 h
F-Ring
F-Ring
F-Ring (außen)140.180014,87 h
🌑 Pandora (81)141.700015,12 h
Pandora
Pandora
 
 Janus/Ephimetheus-Ring  (innere Hälfte, 100 km ~ 17 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
Janus/Epimetheus-Ring (innen)149.000016,30 h
???
???
🌑 Epimetheus (113)151.410016,6640 h
Epimetheus
Epimetheus
🌑 Janus (178)
Janus
Janus
Janus/Epimetheus-Ring (außen)154.000017,13 h
???
???
 
 G-Ring
???
???
G-Ring (innen)166.000019,17 h
???
???
🌑 Aegaeon (0,6)167.500019,43 h
Aigaion
Aigaion
G-Ring (außen)175.000020,75 h
???
???
 
 E-Ring
???
???
E-Ring (innen)180.000021,64 h
E-Ring
E-Ring
🌑 Mimas (397)185.600022,66 h
Mimas
Mimas
🌑 Methone (3)194.000024,22 h
Methone
Methone
Methone-Ringbogen194.230024,26 h
Methone-Ringbogen
Methone-Ringbogen
Anthe-Ringbogen197.665024,91 h
Anthe-Ringbogen
Anthe-Ringbogen
🌑 Anthe (2)197.700024,91 h
Anthe
Anthe
Pallene-Ring (innen)211.000027,5 h
???
???
🌑 Pallene (5)212.280027,7193 h
Pallene
Pallene
Pallene-Ring (außen)213.500028,0 h
???
???
🌑 Enceladus (504)238.040032,8852 h
Enceladus
Enceladus
🌑 Tethys (1062)294.619045,3072 h
Tethys
Tethys
🌑 Telesto (25)
Telesto
Telesto
🌑 Calypso (21)
Calypso
Calypso
🌑 Dione (1123)377.420065,688 h
Dione
Dione
🌑 Helene (35)
Helene
Helene
🌑 Polydeuces (2,5)
Polydeuces
Polydeuces
E-Ring (außen)480.000094 h
E-Ring
E-Ring
🌑 Rhea (1529)527.040108,4386 h
Rhea
Rhea
 
 Phoebe-Ring  (1 Mio. km ~ 20 Pixel)
Vorlage:Panorama/Wartung/Bildbeschreibung fehlt
Vorlage:Panorama/Wartung/Para4
🌑 Iapetus (1436)03,5608 Mio.079,33 d
Iapetus
Iapetus
Phoebe-Ring (innen)04 Mio.095 d
Phoebe-Ring
Phoebe-Ring
🌑 Phoebe (213)12,952 Mio.550,479 d
Phoebe
Phoebe
Phoebe-Ring (außen)13 Mio.550 d
Phoebe-Ring
Phoebe-Ring

Weitere Ring- und Scheibenphänomene in der Astronomie

Deutlich schwächere Ringe finden sich auch bei Jupiter, Uranus und Neptun, den anderen großen Gasplaneten des Sonnensystems. Darüber hinaus sind kreisende Scheiben in der Astronomie ein häufiges Phänomen, das in sehr verschiedenen Größenordnungen auftritt. Neben Planetenringen zählen dazu Akkretionsscheiben bei Röntgendoppelsternen und solche, die sich in der Entstehungsphase von Sternen ausbilden, wie beispielsweise der Asteroidengürtel, aber auch die Spiralgalaxien. Auch hier gilt, dass die Dicke dieser Scheiben durch die Häufigkeit inelastischer Stöße ihrer Komponenten bestimmt wird.

Siehe auch

Weblinks

Commons: Ringe des Saturn – Sammlung von Bildern, Videos und Audiodateien

Einzelnachweise

  1. Ring-a-Round the Saturn auf nasa.gov, abgerufen am 27. Mai 2017
  2. Dorling Kindersley Verlag GmbH: Die Planeten Eine visuelle Reise durch unser Sonnensystem. Dorling Kindersley, München 2015, ISBN 978-3-8310-2830-6, S. 117.
  3. Discovery of inner dark ring of Saturn. In: Monthly Notices of the Royal Astronomical Society. Band 11, S. 20, bibcode:1850MNRAS..11...20B.
  4. Ron Baalke: Historical Background of Saturn's Rings, auf solarviews.com, abgerufen am 27. Mai 2017
  5. International Astronomical Union, Symposium No. 65, Exploration of the Planetary System, herausgegeben von A. Woszczyk, C. Iwaniszewska
  6. M. S. Bobrov: A study of the outermost ring of Saturn auf cambridge.org, abgerufen am 27. Mai 2017
  7. Cassini entdeckt neuen Saturnring (Memento vom 30. September 2007 im Internet Archive) – Meldung bei astronomie.de (Quelle:JPL/NASA (Memento vom 10. Dezember 2007 im Internet Archive))
  8. The King of Rings. NASA, 7. Oktober 2009, archiviert vom Original (nicht mehr online verfügbar) am 10. Oktober 2009; abgerufen am 7. Oktober 2009 (englisch).  Info: Der Archivlink wurde automatisch eingesetzt und noch nicht geprüft. Bitte prüfe Original- und Archivlink gemäß Anleitung und entferne dann diesen Hinweis.@1@2Vorlage:Webachiv/IABot/www.nasa.gov
  9. Nasa-Teleskop entdeckt riesigen Saturnring. Der Spiegel, 7. Oktober 2009, abgerufen am 7. Oktober 2009.
  10. Saturn Riesenring ist noch größer, in scinexx.de, abgerufen: 15. Juni 2016, als Quelle gibt der Artikel an: 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 (11 June 2015)
  11. James Clerk Maxwell: On the stability of the motions of Saturn’s rings. Cambridge 1859 online.
  12. Keller, Hans-Ulrich, Kosmos Himmelsjahr 2009, Stuttgart (Franckh-Kosmos) 2008, ISBN 978-3-440-11350-9; S. 160 u. 180
  13. Ilka Lehnen-Beyel: Blitzartig gestreift. Abgerufen am 2. September 2019., Bild der Wissenschaft zu den rätselhaften Speichen im Ringsystem auf wissenschaft.de, 28. November 2006
  14. C. J. Mitchell u. a.: Saturn's Spokes: Lost and Found. Science, 17. März 2006, Vol. 311. Nr. 5767, S. 1587–1589
  15. Rätselhafte Schlieren: Blitze sollen Saturnringe stören. In: Spiegel Online. 27. November 2006, abgerufen am 27. Februar 2015.
  16. Catalog Page for PIA21437: 'Earhart' Propeller in Saturn's A Ring. In: Photojournal. Jet Propulsions Laboratory, 22. März 2017, abgerufen am 2. Januar 2022.

Auf dieser Seite verwendete Medien

PIA18313 Saturn's D ring and inner C ring - enhanced brightness.jpg
Not all of Saturn's rings are created equal: here the C and D rings appear side-by-side, but the C ring, which occupies the bottom half of this image, clearly outshines its neighbor.

The D ring appears fainter than the C ring because it is comprised of less material. However, even rings as thin as the D ring can pose hazards to spacecraft. Given the high speeds at which Cassini travels, impacts with particles just fractions of a millimeter in size have the potential to damage key spacecraft components and instruments. Nonetheless, near the end of Cassini's mission, navigators plan to thread the spacecraft's orbit through the narrow region between the D ring and the top of Saturn's atmosphere.

This view looks toward the unilluminated side of the rings from about 12 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2015.

The view was acquired at a distance of approximately 372,000 miles (599,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 133 degrees. Image scale is 2.2 miles (3.6 kilometers) per pixel.

The Cassini Solstice Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Solstice Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The original NASA image has been modified by doubling the linear pixel density, cropping, increasing the brightness of the fainter features and converting from TIFF to JPG format.
Iapetus as seen by the Cassini probe - 20071008.jpg

Iapetus as seen by the Cassini probe.
Original NASA caption: Cassini captures the first high-resolution glimpse of the bright trailing hemisphere of Saturn's moon Iapetus.
This false-color mosaic shows the entire hemisphere of Iapetus (1,468 kilometers, or 912 miles across) visible from Cassini on the outbound leg of its encounter with the two-toned moon in Sept. 2007. The central longitude of the trailing hemisphere is 24 degrees to the left of the mosaic's center.
Also shown here is the complicated transition region between the dark leading and bright trailing hemispheres. This region, visible along the right side of the image, was observed in many of the images acquired by Cassini near closest approach during the encounter.
Revealed here for the first time in detail are the geologic structures that mark the trailing hemisphere. The region appears heavily cratered, particularly in the north and south polar regions. Near the top of the mosaic, numerous impact features visible in NASA Voyager 2 spacecraft images (acquired in 1981) are visible, including the craters Ogier and Charlemagne.
The most prominent topographic feature in this view, in the bottom half of the mosaic, is a 450-kilometer (280-mile) wide impact basin, one of at least nine such large basins on Iapetus. In fact, the basin overlaps an older, similar-sized impact basin to its southeast.
In many places, the dark material--thought to be composed of nitrogen-bearing organic compounds called cyanides, hydrated minerals and other carbonaceous minerals--appears to coat equator-facing slopes and crater floors. The distribution of this material and variations in the color of the bright material across the trailing hemisphere will be crucial clues to understanding the origin of Iapetus' peculiar bright-dark dual personality.
The view was acquired with the Cassini spacecraft narrow-angle camera on Sept. 10, 2007, at a distance of about 73,000 kilometers (45,000 miles) from Iapetus.
The color seen in this view represents an expansion of the wavelengths of the electromagnetic spectrum visible to human eyes. The intense reddish-brown hue of the dark material is far less pronounced in true color images. The use of enhanced color makes the reddish character of the dark material more visible than it would be to the naked eye.
This mosaic consists of 60 images covering 15 footprints across the surface of Iapetus. The view is an orthographic projection centered on 10.8 degrees south latitude, 246.5 degrees west longitude and has a resolution of 426 meters (0.26 miles) per pixel. An orthographic view is most like the view seen by a distant observer looking through a telescope.
At each footprint, a full resolution clear filter image was combined with half-resolution images taken with infrared, green and ultraviolet spectral filters (centered at 752, 568 and 338 nanometers, respectively) to create this full-resolution false color mosaic.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
PIA01966 Saturn and its Ring System.jpg
1980: Saturn und seine Ringe
Dione-PIA07746.jpg
Saturnmond Dione, Mosaikbild von der Raumsonde Cassini, Entfernung im Bereich 27 180 bis 55 280km
Enceladusstripes cassini.jpg
Bild von Enceladus, das blaue Rillen oder Spalten auf der Oberfläche zeigt, aufgenommen von der Raumsonde Cassini.
Calypso crop resize sharp.jpg
This raw, unprocessed image of Calypso was taken by Cassini on Feb. 13, 2010.

The image was taken with the Cassini spacecraft narrow-angle camera on Feb. 13, 2010 using a spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The view was obtained at a distance of approximately 23,000 kilometers (14,000 miles) from Calypso. Image scale is 135 meters (443 feet) per pixel.

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Equinox Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The original NASA image has been modified by cropping, doubling the linear pixel density, sharpening and removal of a cosmic ray artifact.
Saturn Colombo-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Colombo-Gap, cropped from Saturn_Ring_C.png
Saturn Encke-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Encke-Gap, crop from Saturn_Ring_A.png
Saturn JanusEphimetheusRing Incomplete.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Crop from 867750_orig.jpg, Shows about the inner 50% of the Janus Ephimetheus Ring
Saturn Rings annotated.jpg
Foto der Ringe des Saturns, fotografiert von der Sonde Cassini aus ca. 1,1 Millionen Kilometer Entfernung.
Image of nothing.svg
Autor/Urheber: Halibutt, Lizenz: CC BY-SA 3.0
nothing
Saturn Ring A inner.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Ring A inner, crop from Saturn_Ring_A.png
Saturn Ring B.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Ring B, cropped Saturn_Rings_annotated.jpg
N00160284.jpg
N00160284.jpg was taken on August 08, 2010 and received on Earth August 09, 2010. The camera was pointing toward ANTHE, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated. A validated/calibrated image will be archived with the NASA Planetary Data System in 2011.
Pan by Cassini, March 2017.jpg
View of the ring shepherd Saturnian moon of Pan, taken from above its northern hemisphere on 7 March 2017 by the Cassini spacecraft. This is a crop of an image by the CL1 and CL2 filters of the Narrow-Angle Imaging Science Subsystem camera, N00277980, that was received on Earth on 8 March.
Saturn LaplaceGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn LaplaceGap
N00163156.jpg
N00163156.jpg was taken on September 13, 2010 and received on Earth September 15, 2010. The camera was pointing toward PALLENE, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated. A validated/calibrated image will be archived with the NASA Planetary Data System in 2011
Saturn Maxwell-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Maxwell-Gap, cropped from Saturn_Ring_C.png
Saturn CassiniDivision+HuygensGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn CassiniDivision+HuygensGap
Saturn's moon Daphnis with wave in ring seen in 2017 by Cassini probe (raw, cropped).jpg
N00274737.jpg was taken on 2017-01-16 13:06 (UTC) and received on Earth 2017-01-18 00:41 (UTC). The camera was pointing toward Daphnis, and the image was taken using the CL1 and GRN filters. This image has not been validated or calibrated. A validated/calibrated image will be archived with the NASA Planetary Data System. (Wikimedia version cropped from original raw image.)

Source URLs: https://saturn.jpl.nasa.gov/raw_images/403840/

http://saturnraw.jpl.nasa.gov/multimedia/images/raw/casJPGFullS97/N00274737.jpg
Tethys PIA07738.jpg
With this full-disk mosaic, Cassini presents the best view yet of the south pole of Saturn's moon Tethys. The giant rift Ithaca Chasma cuts across the disk. Much of the topography seen here, including that of Ithaca Chasma, has a soft, muted appearance. It is clearly very old and has been heavily bombarded by impacts over time. Many of the fresh-appearing craters (ones with crisp relief) exhibit unusually bright crater floors. The origin of the apparent brightness (or "albedo") contrast is not known. It is possible that impacts punched through to a brighter layer underneath, or perhaps it is brighter because of different grain sizes or textures of the crater floor material in comparison to material along the crater walls and surrounding surface. The moon's high southern latitudes, seen here at the bottom, were not imaged by NASA's Voyager spacecraft during their flybys of Tethys 25 years ago. The mosaic is composed of nine images taken during Cassini's close flyby of Tethys (1,071 kilometers, or 665 miles across) on Sept. 24, 2005, during which the spacecraft passed approximately 1,500 kilometers (930 miles) above the moon's surface. This view is centered on terrain at approximately 1.2 degrees south latitude and 342 degrees west longitude on Tethys. It has been rotated so that north is up. The clear filter images in this mosaic were taken with the Cassini spacecraft narrow-angle camera at distances ranging from 71,600 kilometers (44,500 miles) to 62,400 kilometers (38,800 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees. The image scale is 370 meters (1,200 feet) per pixel.
E ring with Enceladus.jpg

Wispy fingers of bright, icy material reach tens of thousands of kilometers outward from Saturn's moon Enceladus into the E ring, while the moon's active south polar jets continue to fire away.

This astonishing, never-before-seen structure is made visible with the sun almost directly behind the Saturn system from Cassini's vantage point. The sun-Enceladus-spacecraft angle here is 175 degrees, a viewing geometry in which structures made of tiny particles brighten substantially.

These features are very likely the result of particles injected into Saturn orbit by the Enceladus geysers: Those injected in the direction of the moon's orbital motion end up on larger, slower orbits and trail Enceladus in its orbit, and those injected into the opposite direction end up smaller, faster orbits and lead Enceladus. (Orbital motion is counter-clockwise.) In addition, the configuration of wisps may hint at an interaction between Saturn's magnetosphere and the torrent of particles issuing from Enceladus.

In addition to the wisps, another unexpected detail is the dark gore in the center of the ring, following the moon in its orbit, likely brought about by the sweeping action of Enceladus as it orbits in the center of the E ring.

The view looks down onto Enceladus (505 kilometers, or 314 miles across) from about 15 degrees above the ringplane. Tethys (1,071 kilometers, or 665 miles across) is visible to the left of Enceladus.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 15, 2006, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Enceladus. Image scale is 128 kilometers (80 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The Cassini imaging team homepage is at http://ciclops.org.

The NASA source image has been cropped on the left side.
Saturn Roche-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Roche Gap, cropped Saturn_Rings_annotated.jpg
Saturn Ring B Outer.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Crop from Saturn_Ring_B.png, Saturn Ring B Outer
Saturn Ring D+beginning Ring C.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
D Ring (left 75%) and beginning C Ring (right 25%) of Saturn, crop from PIA18313 Saturn's D ring and inner C ring - enhanced brightness.jpg
Saturn Surface.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Crop taken from Saturn from Cassini Orbiter (2004-10-06).jpg
PIA09813 Epimetheus S. polar region.jpg

The Cassini spacecraft's close flyby of Epimetheus in December 2007 returned detailed images of the moon's south polar region.

The view shows what might be the remains of a large impact crater covering most of this face, and which could be responsible for the somewhat flattened shape of the southern part of Epimetheus (116 kilometers, or 72 miles across) seen previously at much lower resolution.

The image also shows two terrain types: darker, smoother areas, and brighter, slightly more yellowish, fractured terrain. One interpretation of this image is that the darker material evidently moves down slopes, and probably has a lower ice content than the brighter material, which appears more like "bedrock." Nonetheless, materials in both terrains are likely to be rich in water ice.

The images that were used to create this enhanced color view were taken with the Cassini spacecraft narrow-angle camera on Dec. 3, 2007. The views were obtained at a distance of approximately 37,400 kilometers (23,000 miles) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 65 degrees. Image scale is 224 meters (735 feet) per pixel.

The Cassini–Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini–Huygens mission visit http://saturn.jpl.nasa.gov/home/index.cfm. The Cassini imaging team homepage is at http://ciclops.org.

The NASA image has been cropped.
Mimas Cassini.jpg
Description from NASA :

In this view captured by NASA's Cassini spacecraft on its closest-ever flyby of Saturn's moon Mimas, large Herschel Crater dominates Mimas, making the moon look like the Death Star in the movie "Star Wars."
Herschel Crater is 130 kilometers, or 80 miles, wide and covers most of the right of this image. Scientists continue to study this impact basin and its surrounding terrain (see PIA12569 and PIA12571).
Cassini came within about 9,500 kilometers (5,900 miles) of Mimas on Feb. 13, 2010. This mosaic was created from six images taken that day in visible light with Cassini's narrow-angle camera on Feb. 13, 2010. The images were re-projected into an orthographic map projection. This view looks toward the area between the region that leads on Mimas' orbit around Saturn and the region of the moon facing away from Saturn. Mimas is 396 kilometers (246 miles) across. This view is centered on terrain at 11 degrees south latitude, 158 degrees west longitude. North is up. This view was obtained at a distance of approximately 50,000 kilometers (31,000 miles) from Mimas and at a sun-Mimas-spacecraft, or phase, angle of 17 degrees. Image scale is 240 meters (790 feet) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.
For more information about the Cassini-Huygens mission visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov. The Cassini imaging team homepage is at http://ciclops.org.

The original NASA image has been cropped.
Rhea hi-res PIA07763.jpg
original description: This giant mosaic reveals Saturn's icy moon Rhea in her full, crater-scarred glory. This view consists of 21 clear-filter images and is centered at 0.4 degrees south latitude, 171 degrees west longitude.
Saturn's ring plane.jpg
Ringe des Saturn, die wichtigsten sind gekennzeichnet (NASA).
Methone PIA14633.jpg
It's difficult not to think of an egg when looking at Saturn's moon Methone, seen here during a Cassini flyby of the small moon. The relatively smooth surface adds to the effect created by the oblong shape.

Small moons like Methone are not generally spherical in shape like the larger moons. The closer to Saturn they are, the greater their tidal bulge. Their small sizes means that they lack sufficient gravity to pull themselves into round shape. Scientists think that the elongated shapes of these moons may be a clue to how they formed.

Lit terrain seen here is on the leading side of Methone (2 miles, 3 kilometers across). North on Methone is up. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2012.

The view was obtained at a distance of approximately 3,000 miles (4,000 kilometers) from Methone and at a Sun-Methone-spacecraft, or phase, angle of 63 degrees. Scale in the original image was 88 feet (27 meters) per pixel. The image has been magnified by a factor of 2.

The Cassini Solstice Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

The original NASA image has been modified by cropping and a further doubling of the linear pixel density.
PIA11102-br500.jpg
Recent Cassini images show arcs of material co-orbiting with the Saturnian moons Anthe and Methone.

Arrows indicate the positions of Anthe, at top left, and Methone, at bottom right. Micrometeoroid impacts on the moons are the likely source of the arc material.

Cassini imaging scientists believe the process that maintains the Anthe and Methone arcs is similar to that which maintains the arc in the G ring (see Rounding the Corner). The general brightness of the image (along with the faint horizontal banding pattern) results from the long exposure time of 15 seconds required to capture the extremely faint ring arc and the processing needed to enhance its visibility (which also enhances the digital background noise in the image). The image was digitally processed to remove most of the background noise. This view looks toward the un-illuminated side of the rings from about 2 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 29, 2007. The view was acquired at a distance of approximately 2.3 million kilometers (1.4 million miles) from Anthe and 2.2 million kilometers (1.4 million miles) from Methone. Image scale is 14 kilometers (9 miles) per pixel on Anthe and 13 kilometers (8 miles) on Methone.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .
Polydeuces.jpg
Polydeuces, moon of Saturn
Saturn RusselllGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn RusselllGap
Saturn Ring A outer+Keeler-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Ring A outer+Keeler-Gap, crop from Saturn_Ring_A.png
A Ring propeller "Santos-Dumont" (PIA 21433).jpg

Uploader's notes: the original NASA image has been modified by cropping, removal of artifacts and converting from TIFF to JPG format.

Original caption released with image:

NASA's Cassini spacecraft captured these remarkable views of a propeller feature in Saturn's A ring on Feb. 21, 2017. These are the sharpest images taken of a propeller so far, and show an unprecedented level of detail. The propeller is nicknamed "Santos-Dumont," after the pioneering Brazilian-French aviator.

This observation was Cassini's first targeted flyby of a propeller. The views show the object from vantage points on opposite sides of the rings. The top image looks toward the rings' sunlit side, while the bottom image shows the unilluminated side, where sunlight filters through the backlit ring.

The two images presented as figure A are reprojected at the same scale (0.13 mile or 207 meters per pixel) in order to facilitate comparison. The original images, which have slightly different scales, are also provided here, without reprojection, as figure B; the sunlit-side image is at left, while the unlit-side image is at right.

Cassini scientists have been tracking the orbit of this object for the past decade, tracing the effect that the ring has upon it. Now, as Cassini has moved in close to the ring as part of its ring-grazing orbits, it was able to obtain this extreme close-up view of the propeller, enabling researchers to examine its effects on the ring. These views, and others like them, will inform models and studies in new ways going forward.

Like a frosted window, Saturn's rings look different depending on whether they are seen fully sunlit or backlit. On the lit side, the rings look darker where there is less material to reflect sunlight. On the unlit side, some regions look darker because there is less material, but other regions look dark because there is so much material that the ring becomes opaque.

Observing the same propeller on both the lit and unlit sides allows scientists to gather richer information about how the moonlet affects the ring. For example, in the unlit-side view, the broad, dark band through the middle of the propeller seems to be a combination of both empty and opaque regions.

The propeller's central moonlet would only be a couple of pixels across in these images, and may not actually be resolved here. The lit-side image shows that a bright, narrow band of material connects the moonlet directly to the larger ring, in agreement with dynamical models. That same thin band of material may also be obscuring the moonlet from view.

Lengthwise along the propeller is a gap in the ring that the moonlet has pried open. The gap appears dark on both the lit and unlit sides. Flanking the gap near the moonlet are regions of enhanced density, which appear bright on the lit side and more mottled on the unlit side.

One benefit of the high resolution of these images is that, for the first time, wavy edges are clearly visible in the gap. These waves are also expected from dynamical models, and they emphasize that the gap must be sharp-edged. Furthermore, the distance between the wave crests tells scientists the width of the gap (1.2 miles or 2 kilometers), which in turn reveals the mass of the central moonlet. From these measurements, Cassini imaging scientists deduce that the moonlet's mass is comparable to that of a snowball about 0.6 mile (1 kilometer) wide.

For the original images (figure B), the lit-side image has a scale of 0.33 mile (530 meters) per pixel in the radial (or outward from Saturn) direction and 0.44 mile (710 meters) per pixel in the azimuthal (or around Saturn) direction. The different scales are the result of Cassini's vantage point being off to the side of the propeller, rather than directly above it. The unlit-side image has a scale of 0.25 (410 meters) per pixel in both directions.

In order to preserve its original level of detail, the image has not been cleaned of bright blemishes due to cosmic rays and to charged particle radiation from Saturn.

The Cassini Solstice Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Solstice Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.
PIA12593 Prometheus2.jpg
Cassini spacecraft image of Prometheus, one of Saturn's small inner moons. Appearing like eyes on a potato, craters cover the dimly lit surface of the moon Prometheus in this high-resolution image from Cassini's early 2010 flyby.

The Jan. 27 encounter represented the closest imaging sequence yet of that moon for Cassini. This view looks toward the trailing hemisphere of Prometheus (86 kilometers, 53 miles across). North on Prometheus is up and rotated 8 degrees to the right.

The moon is lit by sunlight on the right and Saturnshine on the left.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 27, 2010. The view was obtained at a distance of approximately 34,000 kilometers (21,000 miles) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 126 degrees. Image scale is 200 meters (658 feet) per pixel.

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Equinox Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The original NASA image has been modified by cropping and brightening shadows. A version in which shadows are brightened less is here.
Cassini Atlas N00084634 CL.png
Narrow Angle Camera image of Atlas. Adapted from source images. Imaged from 181,000 km with clear filters, about 1km per pixel.
Saturn Ring C Inner.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Inner part of the C Ring of Saturn, crop from D_ring_structure.jpg
Saturn Ring C.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Ring C, cropped Saturn_Rings_annotated.jpg
Saturn Bessel+BernardGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn_Bessel+BernardGap
Saturn Ring C Outer.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Outer part of the C Ring of Saturn, cropped from Saturn_Ring_C.png
Saturn Roche-Gap outer.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Roche-Gap outer, crop from Saturn_Roche-Gap.png
Saturn Ring A.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Ring A, cropped Saturn_Rings_annotated.jpg
Saturn Cassini-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Cassini-Gap, cropped Saturn_Rings_annotated.jpg
Rsz aigaion from cassini.jpg
W00062681.jpg was taken on January 27, 2010 and received on Earth January 28, 2010. The camera was pointing toward AEGAEON, and the image was taken using the CL1 and CL2 filters. This image has not been validated or calibrated. A validated/calibrated image will be archived with the NASA Planetary Data System in 2011.
Pandora PIA07632.jpg
NASA description:
Cassini acquired infrared, green and ultraviolet images on Sept. 5, 2005, which were combined to create this false-color view. The image was taken with the Cassini spacecraft narrow-angle camera at a distance of approximately 52,000 kilometers (32,000 miles) from Pandora and at a Sun-Pandora-spacecraft, or phase, angle of 54 degrees. Resolution in the original image was about 300 meters (1,000 feet) per pixel. The image has been magnified by a factor of two to aid visibility.
Saturn JeffreysGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn JeffreysGap
Saturn Dawes-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Dawes-Gap, cropped from Saturn_Ring_C.png
Saturn CassiniDivision Outer.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn CassiniDivision Outer Part
Saturn Roche-Gap inner.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Roche-Gap inner, crop from Saturn_Roche-Gap.png
PIA12714 Janus crop.jpg
Saturn's moon Janus shows the scars of impacts in this Cassini image of craters light and dark.

This view looks toward the Saturn-facing side of Janus (179 kilometers, 111 miles across). North on Janus is up and rotated 10 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 7, 2010. The view was acquired at a distance of approximately 75,000 kilometers (46,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 39 degrees. Image scale is 448 meters (1,469 feet) per pixel.

The original NASA image has been modified by cropping, doubling the linear pixel density, and sharpening.
PIA12758 Helene crop.jpg
Cassini imaged the surface of Saturn's moon Helene as the spacecraft flew by the moon on Jan. 31, 2011.

This small moon leads Dione by 60 degrees in the moons' shared orbit. Helene is a "Trojan" moon of Dione, named for the Trojan asteroids that orbit 60 degrees ahead of and behind Jupiter as it circles the Sun. See PIA12723 for an earlier, closer view.

This view looks toward the leading hemisphere of Helene (33 kilometers, 21 miles across). North on Helene is up and rotated 2 degrees to the left.

The image was taken with the Cassini spacecraft narrow-angle camera using a combination of spectral filters sensitive to wavelengths of polarized green light centered at 617 and 568 nanometers. The view was obtained at a distance of approximately 31,000 kilometers (19,000 miles) from Helene and at a Sun-Helene-spacecraft, or phase, angle of 65 degrees. Scale in the original image was 187 meters (612 feet) per pixel. The image was contrast enhanced and magnified by a factor of 1.5 to enhance the visibility of surface features.

The Cassini Solstice Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Solstice Mission visit http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

The original NASA image has been modified by cropping, doubling the linear pixel density, sharpening, lightening shadows and increasing contrast.
Saturn KuiperGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn KuiperGap
Voyager 2 - Saturn Rings - 3085 7800 2.png
Voyager 2 obtained this high-resolution picture of Saturn's rings Aug. 22, 1981, when the spacecraft was 4 million kilometers (2.5 million miles) away. Evident here are the numerous "spoke" features, in the B-ring; their very sharp, narrow appearance suggests short formation times. Scientists think electromagnetic forces are responsible in some way for these features, but no detailed theory has been worked out. Pictures such as this and analyses of Voyager 2's spoke movies may reveal more clues about the origins of these complex structures.
Phoebering2.jpg
This diagram illustrates the extent of the largest ring around Saturn, discovered by NASA's Spitzer Space Telescope.
Saturn Ring D outer.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Outer part of Saturn's D ring
Phoebe cassini.jpg
Phoebe, as imaged by the Cassini probe.
Saturn largest ring Spitzer telescope 20091006.jpg
This artist's conception shows a nearly invisible ring around Saturn — the largest of the giant planet's many rings. It was discovered by NASA's Spitzer Space Telescope.
Saturn HerschelGap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
crop from Saturn_Cassini-Gap.png, Saturn HerschelGap
Saturn Ring B inner.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Crop from Saturn_Ring_B.png, Saturn Ring B inner
Ring Phoebe2.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Phoebe Ring, tiled/croped from Phoebering2.jpg
Saturn Ring D inner.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Inner part of Saturn's D ring
Saturnoppositions.jpg
Autor/Urheber: The Saturn views were simulated with a computer program written by Tom Ruen (created here for public domain)., Lizenz: CC BY-SA 3.0
This sequence of simulated views demonstrates the 29.5-year orbital period of Saturn by opposition date, as well as the dramatic changes in the orientation of the planet's ring disk. The ring system revolves around a fixed axis, so both sides of the ring disk are visible from Earth during each period in which Saturn orbits the Sun.

(Note: If viewed with a parallel view stereo technique, this set of images provides a pretty plastic 3D effect to the viewer.)

Reference
  • Meeus, Jean (1988) Astronomical Formulae for Calculators (4th Aufl.), Willmann-Bell
External sources
Saturn Bond-Gap.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn Bond-Gap, cropped from Saturn_Ring_C.png
Saturn from Cassini Orbiter (2004-10-06).jpg
While cruising around Saturn in early October 2004, Cassini captured a series of images that have been composed into the largest, most detailed, global natural color view of Saturn and its rings ever made.

This grand mosaic consists of 126 images acquired in a tile-like fashion, covering one end of Saturn's rings to the other and the entire planet in between. The images were taken over the course of two hours on Oct. 6, 2004, while Cassini was approximately 6.3 million kilometers (3.9 million miles) from Saturn. Since the view seen by Cassini during this time changed very little, no re-projection or alteration of any of the images was necessary.

Three images (red, green and blue) were taken of each of 42 locations, or "footprints," across the planet. The full color footprints were put together to produce a mosaic that is 8,888 pixels across and 4,544 pixels tall.

The smallest features seen here are 38 kilometers (24 miles) across. Many of Saturn's splendid features noted previously in single frames taken by Cassini are visible in this one detailed, all-encompassing view: subtle color variations across the rings, the thread-like F ring, ring shadows cast against the blue northern hemisphere, the planet's shadow making its way across the rings to the left, and blue-grey storms in Saturn's southern hemisphere to the right. Tiny Mimas and even smaller Janus are both faintly visible at the lower left.

The Sun-Saturn-Cassini, or phase, angle at the time was 72 degrees; hence, the partial illumination of Saturn in this portrait. Later in the mission, when the spacecraft's trajectory takes it far from Saturn and also into the direction of the Sun, Cassini will be able to look back and view Saturn and its rings in a more fully-illuminated geometry.
Saturn eclipse (cropped).jpg
Saturn eclipsing the sun, seen from behind from the Cassini orbiter. The image is a composite assembled from images taken by the Cassini spacecraft on 15 September, 2006.

Individual rings seen include (in order, starting from most distant)

  • E ring
  • Pallene ring (visible very faintly in an arc just below Saturn)
  • G ring
  • Janus/Epimetheus ring (faint)
  • F ring (narrow brightest feature)
  • Main rings (A,B,C)
  • D ring (bluish, nearest Saturn)
PIA11665 moonlet in B Ring cropped.jpg
The Cassini spacecraft captured this image of a small object in the outer portion of Saturn's B ring casting a shadow on the rings as Saturn approaches its August 2009 equinox.
Saturn Ring F.png
Autor/Urheber: Frank Klemm, Lizenz: CC BY-SA 4.0
Saturn F Ring, cropped Saturn_Rings_annotated.jpg
PIA11101 Anthe ring arc.jpg
Cassini images reveal the existence of a faint arc of material orbiting with Saturn's small moon Anthe.

The moon is moving downward and to the right in this perspective. In this image, most of the visible material in the arc lies ahead of Anthe (2 kilometers, or 1 mile across) in its orbit. However, over time the moon drifts slowly back and forth with respect to the arc. The arc extends over about 20 degrees in longitude (about 5.5 percent of Anthe's orbit) and appears to be associated with a gravitational resonance caused by the moon Mimas. Micrometeoroid impacts on Anthe are the likely source of the arc material. The orbit of Anthe lies between the larger moons Mimas and Enceladus. Anthe shares this region with two other small moons, Pallene (4 kilometers, or 3 miles across) and Methone (3 kilometers, or 2 miles across). Methone also possesses an arc (see PIA11102), while Pallene is known to orbit within a faint, complete ring of its own (see PIA08328).

Cassini imaging scientists believe the process that maintains the Anthe and Methone arcs is similar to that which maintains the arc in the G ring (see PIA08327). The general brightness of the image (along with the faint horizontal banding pattern) results from the long exposure time of 32 seconds required to capture the extremely faint ring arc and the processing needed to enhance its visibility (which also enhances the digital background noise in the image). The image was digitally processed to remove most of the background noise. The long exposure also produced star trails in the background. This view looks toward the un-illuminated side of the rings from about 3 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 3, 2008. The view was obtained at a distance of approximately 1.2 million kilometers (739,000 miles) from Anthe and at a sun-Anthe-spacecraft, or phase, angle of 12 degrees. Image scale is 7 kilometers (4 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

The original NASA image has been resized and cropped.