Saturne
Saturn orbits the Sun at an average distance of 9.5 astronomical units, or 1.4 billion kilometers. Second planet in size with a diameter of 121,000 kilometers, it is best known for its beautiful rings.
Like Jupiter, it rotates very fast on itself in about ten hours, and consists mainly of hydrogen and helium, as evidenced by its low density of only 0.69 times that of water .
The planet has been studied in detail by four probes: Pioneer 11 in 1979, Voyager 1 in 1980 and Voyager 2 in 1981 and especially since 2004 Cassini-Huygens.
These have revealed the complexity of the rings and have provided high-resolution images of the visible surface of Saturn. The latter has proved far less colorful than that of Jupiter, albeit with parallel yellow stripes at the equator and some white spots.
The internal structure of Saturn
Saturn has a similar internal structure of Jupiter. A stronger flattening of the world suggests that the rocky core is larger. The weaker magnetic field indicates that meanwhile the metallic hydrogen layer is to be thinner.
The upper part of the atmosphere is also similar to that of Jupiter, with the same three layers (NH3, and H2O NH4SH) and a parallel band structure at the equator.
The lack of color and contrast is due to the lower gravity of Saturn, which makes the three layers are spread over several hundred kilometers, instead of several tens of kilometers to Jupiter. The deep layers are thus masked by hundreds of kilometers of haze.
Like its neighbor, Saturn emits more energy than it receives, ie 2.5 times. This is probably not due to the energy accumulated during the training phase, but rather to helium falls inward of the planet, similar to our rainfall. These movements are transforming gravitational energy into heat and can also explain the low helium concentration in the outer layers.
Saturn's rings
Saturn's rings were observed for the first time by Galileo in 1610, which took the two satellites of the planet. Christian Huygens described the ring as a single in 1655. They were not identified as many rings as a few years later, in particular by Cassini in 1675 which identified the discontinuity that bears his name.
The rings have an external diameter of about 600 000 km and a thickness of just 2 km. The images taken by the sensors show that the relatively wide rings that can be seen from the Earth are in fact formed of a multitude of very fine and very close rings.
These thin rings are themselves composed of a myriad of small independent solid bodies in orbit around the planet faster and even turn they are close to Saturn. These bodies consist essentially of ice or ice-covered rock. Their size varies between one millimeter and several tens of meters.
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