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 |  planets  8 planets of the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) and their satellites. |  sun The Sun is in 2/3 of the galactic center towards the edge, at a distance of 30 000 light years of the center. The Sun moves in a speed of 230 km/s around this galactic center during its revolution which it makes in 250 million years. |  galaxies The Galaxy, it is the name datum in our galaxy, it is an enormous spiral wheel of stars, a diameter of 100 000 light years. What appears of the Earth, it is a white continuous band called the Milky Way. |  bigbang There is 15 billion years a tremendous explosion of light gives birth to the space, in time, in the matter, a chaos burning with an inconceivable heat, a formless porridge which is going to swell, to extend in all the directions and to cool quite slowly. |  quotations Some quotations of big men (Aristote, Galilee, Newton, Platon, Laplace, Einstein). |  links Some external links concerning the astronomy.

|
|  |  dwarf planets According to the definition which was approved on August 24th, 2006, during the 26th General assembly of the UAI ( International Astronomical Union), three bodies reach the status of dwarfish planet: Pluto, eris, and Ceres. Others objets should soon join this nomenclature. |  solar system The solar system is really much more complex if we take into account all the objects being a part of the system. A considerable number of objects is in the belt of Kuiper and still beyond in the cloud of Oort. |  galaxy groups Heap of galaxies are the biggest structures of the Universe. They are constituted by hundreds of galaxies connected together by their own gravitational attraction. Between the galaxies we find some material constituted by warm gas there, forming a plasma, the temperature of which reaches 10 to 100 million degrees. |  comets Besides planets, satellites and asteroids, the solar system contains comets (hair in Greek). The roaming comets originate in the depths of the space in several lights years. The number of periodic comets is of the order of 2000. |  biographies Some biographies, Einstein, Baade, Lyot, Hale, Hubble, Shapley, Laplace, Maxwell, Newton, Herschel, Kepler, Galilee, Aristotle... |  glossary Definition of certain words or expressions used on this site in link with the astronomy.

 |
| articles Christian's articles in link with the astronomy (history of the Earth, the electron, the neutrons stars, the rings of Saturn, the particles, the threat of asteroids, journey in the universe up to the atom)... |  exoplanets Exoplanets are situated by definition outside our solar system. Seen the large number of existing galaxies and the large number of stars which they contain, the search for these exo-planets or extra solar planets, is unlimited. |  constellations A constellation is a group of stars of the sky which enough close relations looked the appearance imagination of a figure onto the sky. |  nebulas Of the Latin 'nebula' which wants to say cloud, clouds of gas and dusts in the middle of stars, nebulas are at the same moment active crèches and cemeteries of stars. These magnificence of the sky are lit by the stars which they contain or by stars situated behind them. |  telescopes A telescope is constituted by a mirror which concentrates the light resulting from the observed celestial body and from the objective which supplies an enlarged image with it. The increase and the luminosity are proportional on the surface of the mirror. The presence of the ground atmosphere limits the performances of a telescope. It is to mitigate this inconvenience that spatial telescopes were placed in the space. |  bibliographies Some interesting books in link with the astronomy. |  faq Some simple answers concerning the universe which surrounds us.

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| asteroids Numerous small rocky called bodies asteroids are present in the solar system, an important part of them circulate in a ring, between the orbit of Mars and that of Jupiter in 2 to 4 UA.

 |  rings The rings of Saturn are one of more beautiful and of the most surprising spectacles of the solar system. That is why on July 1st, 2004, the spaceship Cassini-Huygens reduced its speed to be captured by the gravity of Saturn to enter in orbit with this one. |  stars A star is a celestial body similar to the Sun, which shines thanks to nuclear reactions which occur in its center. |  multiverse The universe is an expanding cosmic bubble. This bubble creates a new bubble which produces it the others etc.... Quantities of the other universes which give birth to the other universes, it is an interesting idea but which remain at the moment very speculative. |  space probes These instruments that are space probes, perceive in the detail the forms and the composition of objects of the distant regions and offer us exceptional sights of an unequalled precision. |  elements The most usual and practical presentation of the diverse chemical elements is the periodic board of elements also called Table of Mendeleyev. The atoms which have the same number of protons but a number different from neutrons are called isotopes. |  aurora A polar aurora called aurora borealis in the north hemisphere and the aurora australis in the southern hemisphere, is a brilliant phenomenon characterized by sorts of veils extremely colored in the night-sky.

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 The universe is all worked up Imprimer cette page


Rings of Saturn

      

         
automatic translator        
The mission Cassini-Huygens      

category: saturn - planet

       

The rings of Saturn are one of beautiful and of the most surprising spectacles of the solar system. That is why on July 1st, 2004, the spaceship Cassini-Huygens reduced its speed to be captured by the gravity of Saturn to enter in orbit with this one. The spaceship will investigate until 2008 the planet, its mysterious moons, its stunning rings and its magnetic environment gives a complex. Cassini has to make 74 rotations around the planet, get closer to Titan and the other icy moons of Saturn. The most beautiful of the spectacles is the one all the same that propose us the rings of Saturn, each on his orbit, all aligned in a fine band of some kilometers...
The mission Cassini-Huygens is a cooperative project between the NASA, the European Space agency and the Italian Space agency. JPL, is the division of the Technological Institute of California to Pasadena, who manages the mission Cassini-Huygens for the Direction of the NASA, in Washington. The space shuttle Cassini was conceived, developed and assembled by JPL.

  

[ Photography taken with the camera of the spaceship Cassini on December 17th, 2006 at a rough distance of 1.1 million kilometers of Saturn. The scale of image is 64 kilometers by pixel.]

  

         

The origin of rings

       category: saturn - planet  
       

The rings of Saturn are constituted by uncountable particles, each on an appropriate orbit, of silicates, oxide of iron and particles of ice of a size varying of the speck of dust in some meters. Rings extend over a fine layer of more than 400 000 km. With the exception of the most external ring, they do not exceed 1 km in thickness. All this matter combined in a single object, would be equivalent to the size of Epimetheus Epimetheus Placed on the same orbit as Janus, measures only 138x110x110 km. The shape of this satellite is very irregular and its surface presents big valleys. We can perceive several craters there furthermore of 30 kilometers wide.  or of Prometheus Prometheus is an irregular satellite of Saturn of a size of 148×100×68 km. It presents numerous valleys and cliffs as well as several craters of about twenty kilometers in diameter. It seems less craterised than the nearby moons, Pandore, Janus and Epimetheus. Its weak density and its high albedo seem to indicate that Prometheus is a very porous celestial body of ice. The observations of the 1995s and 1996 put in evidence that Prometheus was late of 20 ° with regard to its position of 1981. This distance cannot explain by errors of observations. It is thus possible that the orbit of Prometheus changed following a collision or that it possesses the moon partner who shares her orbit.  that is no bigger than the moon from 100 to 150 km in diameter. The theory proposed by Édouard Albert Roche in the 19th century, explains that rings result from the moon of Saturn the orbit of which would have too much got closer to the planet and which would have been broken by the strengths of tide either split by the impact of a comet or an asteroid.

 

The rings of Saturn are too unstable to last, they thus have a recent origin in the astronomical scale. Since the Earth we can observe three rings, rings (In and B) and a ring more thin. The zone enters A and B is known under the name of division of Cassini. The ring A is divided by a less visible space named division of Encke. Voyager probes detected four other much less visible rings. The ring F, one of the most external, has an extremely complex structure of several interlaced smaller rings. The origin of these knots is unknown but is probably gravitational. The ring E, the most external, extends over 300 000 km and widens gradually after the orbit of Enceladus until reach 60000 km in thickness. Noted: the equatorial diameter of Saturn is 120536 km.

  

Name

 internal beam (km) width
(km)
ring D 66 900 7 610
division of Guérin 74 510 148
ring C 74 658 17 342
ring B 92 000 25 580
division of Cassini 117 500 4 700
ring A 122 170 14 605
division of Encke 133 589 325
division of Keeler 136 530 35
R/2004 S 1 137 630 300
R/2004 S 2 138 900  
ring F 140 180 30 - 500
ring G 170 000 5 000
ring E 181 000 302 000
         

A complex system

      

category: saturn - planet 

       

The rings of Saturn maintain complex echo with some of its satellites. Some, named 'satellite shepherds' (Atlas, Prometheus and Pandora), is clearly indispensable for the stability of rings. Mimed seems responsible for the division of Cassini, Piece is situated inside the division of Encke. The global system is of a very big complexity as shows it the results of the probe Cassini, entered the orbit of Saturn in 2004. This complex and surprising planetary system intrigues the scientists. One of these intrigues concerns the division Cassini, that is the big interval situated between rings A and B. While the rings of Saturn almost exclusively consist of water in the form of ice, the data show that the division of

  

Cassini contains more dusts than ice. The division Cassini discovered to 17th century by Giovanni Domenico Cassini, revealed that the rings of Saturn did not constitute adjoining elements. Particles situated between rings A and B look like outstandingly what was observed on Phoebe, one of the moons of Saturn. These black particles relaunch the theory according to which rings would be the rests of the split moon. The Cassini probe detected big quantities of oxygen around rings. This phenomenon could explain by a collision which would have provoked this substantial separation of oxygen.
[Photography taken by the Voyager probe 2, on August 22nd, 1981]

  

         

The limit of Rock

      

category: saturn - planet 

       

What of what it is necessary to take into account it is the nearness of rings with regard to its planet. Indeed the zone of rings is hardly situated between 60 and 200 000 km of the planet while Saturn has an equatorial diameter of 120 536 km. What explains the instability of its structures in rings. Its structures of particles can thus exist only in a perimeter defined well inside the limit of Rock maintained by the strong attraction of the close planet. Near the planet, the strengths of attraction of the planet on two close particles is superior to the mutual attraction between both particles, what prevents the accretion of particles. The distance in which these two effects nullify is called the limit of Rock. Beyond, the collisions bring particles to cling by accretion and to form a satellite. Since the Earth this structure seems homogeneous but closer rings show different bands. Closer still, we would see uncountable free particles which would disappear very quickly if no mechanism maintained them in place. It is there that bring in in track satellites guards.

 

This role of sculptor and guard of these structures is mainly played by these satellites. The rings of Saturn have less than one kilometer in thickness and can locally, to be much thinner. Indeed, the collisions tend to reduce the perpendicular movements to the equatorial plan. The natural shape of a ring thus is to be flat and wide, to spread regularly until the limit of Rock. All the objects going out of this zone are transformed into satellite. The origin of rings stays one of the most difficult problems which settles to the astronomers. As far as it is not about a unique phenomenon. Jupiter, Uranus and Neptune possess too systems of comparable rings.
[The photography opposite is constituted by an assembly of clichés begun by Travelling 2 at a distance of 21 million km. Three visible satellites of Saturn to the left are from top to bottom: Tethys (1050 km in diameter), Dione (1120 km), and Rhea (1530 km). To note the shadow of Tethys which forms a blackhead on the planet.]

  

         

Related subjects

      

category: saturn - planet

       

Téthys

   Lapetus    

Enceladus

   Rhea    
Dione   Titan    

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 |  planets  8 planets of the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) and their satellites. |  sun The Sun is in 2/3 of the galactic center towards the edge, at a distance of 30 000 light years of the center. The Sun moves in a speed of 230 km/s around this galactic center during its revolution which it makes in 250 million years. |  galaxies The Galaxy, it is the name datum in our galaxy, it is an enormous spiral wheel of stars, a diameter of 100 000 light years. What appears of the Earth, it is a white continuous band called the Milky Way. |  bigbang There is 15 billion years a tremendous explosion of light gives birth to the space, in time, in the matter, a chaos burning with an inconceivable heat, a formless porridge which is going to swell, to extend in all the directions and to cool quite slowly. |  quotations Some quotations of big men (Aristote, Galilee, Newton, Platon, Laplace, Einstein). |  links Some external links concerning the astronomy.

|
|  |  dwarf planets According to the definition which was approved on August 24th, 2006, during the 26th General assembly of the UAI ( International Astronomical Union), three bodies reach the status of dwarfish planet: Pluto, eris, and Ceres. Others objets should soon join this nomenclature. |  solar system The solar system is really much more complex if we take into account all the objects being a part of the system. A considerable number of objects is in the belt of Kuiper and still beyond in the cloud of Oort. |  galaxy groups Heap of galaxies are the biggest structures of the Universe. They are constituted by hundreds of galaxies connected together by their own gravitational attraction. Between the galaxies we find some material constituted by warm gas there, forming a plasma, the temperature of which reaches 10 to 100 million degrees. |  comets Besides planets, satellites and asteroids, the solar system contains comets (hair in Greek). The roaming comets originate in the depths of the space in several lights years. The number of periodic comets is of the order of 2000. |  biographies Some biographies, Einstein, Baade, Lyot, Hale, Hubble, Shapley, Laplace, Maxwell, Newton, Herschel, Kepler, Galilee, Aristotle... |  glossary Definition of certain words or expressions used on this site in link with the astronomy.

 |
| articles Christian's articles in link with the astronomy (history of the Earth, the electron, the neutrons stars, the rings of Saturn, the particles, the threat of asteroids, journey in the universe up to the atom)... |  exoplanets Exoplanets are situated by definition outside our solar system. Seen the large number of existing galaxies and the large number of stars which they contain, the search for these exo-planets or extra solar planets, is unlimited. |  constellations A constellation is a group of stars of the sky which enough close relations looked the appearance imagination of a figure onto the sky. |  nebulas Of the Latin 'nebula' which wants to say cloud, clouds of gas and dusts in the middle of stars, nebulas are at the same moment active crèches and cemeteries of stars. These magnificence of the sky are lit by the stars which they contain or by stars situated behind them. |  telescopes A telescope is constituted by a mirror which concentrates the light resulting from the observed celestial body and from the objective which supplies an enlarged image with it. The increase and the luminosity are proportional on the surface of the mirror. The presence of the ground atmosphere limits the performances of a telescope. It is to mitigate this inconvenience that spatial telescopes were placed in the space. |  bibliographies Some interesting books in link with the astronomy. |  faq Some simple answers concerning the universe which surrounds us.

 |

| asteroids Numerous small rocky called bodies asteroids are present in the solar system, an important part of them circulate in a ring, between the orbit of Mars and that of Jupiter in 2 to 4 UA.

 |  rings The rings of Saturn are one of more beautiful and of the most surprising spectacles of the solar system. That is why on July 1st, 2004, the spaceship Cassini-Huygens reduced its speed to be captured by the gravity of Saturn to enter in orbit with this one. |  stars A star is a celestial body similar to the Sun, which shines thanks to nuclear reactions which occur in its center. |  multiverse The universe is an expanding cosmic bubble. This bubble creates a new bubble which produces it the others etc.... Quantities of the other universes which give birth to the other universes, it is an interesting idea but which remain at the moment very speculative. |  space probes These instruments that are space probes, perceive in the detail the forms and the composition of objects of the distant regions and offer us exceptional sights of an unequalled precision. |  elements The most usual and practical presentation of the diverse chemical elements is the periodic board of elements also called Table of Mendeleyev. The atoms which have the same number of protons but a number different from neutrons are called isotopes. |  aurora A polar aurora called aurora borealis in the north hemisphere and the aurora australis in the southern hemisphere, is a brilliant phenomenon characterized by sorts of veils extremely colored in the night-sky.

|
 The universe is all worked up Imprimer cette page


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Astronomy - october 15th 2007