Saturn It is the second largest planet in the Solar System and the only one with rings visible from Earth. It is clearly marked by the poles because of the rapid rotation.
The name of the planet comes from the Roman god of agriculture, Saturn, father of Jupiter. Its Greek equivalent was Cronos, father of Zeus. As Saturn moves through the sky three times slower than Jupiter, ancient astronomers naturally identified him with his elderly father.
It is one of the four gas giants, all of them planets with rings, although those of Saturn are larger and brighter. Before the telescope was invented it was the farthest known planet.
It has a rocky core surrounded by hydrogen, with a little helium and methane. It radiates more heat than it receives from the Sun, as is the case with the giants Jupiter and Neptune. The yellowish color of the clouds has bands of other colors, such as Jupiter, but not as marked. Near the equator of Saturn the wind blows at more than 450 km / h.
The following table shows Saturn data compared to Earth:
|Basic data||Saturn||The earth|
|Size: equatorial radius||58.232 km.||6,378 km.|
|Average distance to the Sun||1,426,725,400 km.||149,600,000 km.|
|Day: period of rotation on the axis||10.23 hours||23.93 hours|
|Year: orbit around the Sun||29.46 years||1 year|
|Average surface temperature||-139 º C||15 º C|
|Surface gravity in the equator||9.1 m / s2||9.78 m / s2|
It is the only planet in the Solar System that has a lower density than water. If we found an ocean large enough, Saturn would float.
Galileo first observed the rings in 1610, but confused them with satellites since his telescope was still rudimentary. In 1659 Christiaan Huygens, with an improved telescope, saw them clearly and without doubts. It took two centuries until, in 1859, James Clerk Maxwell demonstrated mathematically that the rings of Saturn were formed by particles. Until then it was believed that they were solid.
The rings give Saturn a very beautiful appearance. It has two bright, A and B, and one softer, C. Among them there are openings. The biggest is the Cassini Division. Each main ring consists of many narrow rings. Its composition is uncertain, but we know that contain water. They could be icebergs or snowballs, mixed with dust.
In 1850, astronomer Edouard Roche studied the effect of the gravity of the planets on their satellites, and calculated that any matter located less than 2.44 times the radius of the planet could not agglutinate to form a body, and, if already It was a body, it would break.
The inner ring of Saturn, C, is at 1.28 times the radius, and the outer one, the A, at 2.27. The two are within the Roche limit, but their origin has not yet been determined. With the matter they contain, a sphere of a size similar to that of the Moon could be formed.
The elaborate structure of the rings was attributed in principle to the gravity force of nearby satellites, in combination with the centrifugal force generated by Saturn's own rotation. However, Voyager probes discovered dark structures that could not be explained like this. These structures rotate on the rings at the same speed as the planet's magnetosphere, so they could interact with their magnetic field.
The particles that make up Saturn's rings have sizes ranging from microscopic measurements to pieces like a house. Over time, they are collecting remains of comets and asteroids. A good part of the material that forms them is ice. If they were very old, they would be dark because of the accumulation of dust. The fact that they are bright indicates that they are young.
In 2006 the Cassini ship He discovered a new ring while traveling on the opposite side of the Sun, in the shadow of Saturn. Solar concealment allowed to detect particles that are not usually visible. The ring, located between the F and G, coincides with the orbits of Janus and Epimetheus, two satellites that almost share their orbits and periodically exchange them. Perhaps the impacts of meteors on those moons are providing the particles that form the ring.
In fact, all the rings could have been formed from satellites that suffered impacts from comets and meteoroids. In 2017 the Cassini probe passed between Saturn and its nearest ring, located about 2000 km. This ship is, for the moment, one of the most important sources of data and images on the planet. However, four hundred years after its discovery, the impressive rings of Saturn are still shrouded in mystery.
• In pictures: Cassini's amazing trip to Saturn
• Saturn's Hexagon
• Biography of Giovanni Doménico Cassini
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