Planetary Ring

A planetary ring is a ring made up of dust and other small particles orbiting around a planet in an area in the shape of flat disc. The most spectacular and known planetary rings are those of Saturn but each of the four giant gas of the Solar system (Jupiter, Saturn, Uranus and Neptune) has a system of rings.

Origin

The origin of the planetary rings is not known with certainty (they could be the result of a tearing off of continuous material or were already present as of the formation of planet), and it is generally estimated that they are unstable and disperse little by little in a few tens or hundreds of million years. Thus, the systems of rings known today are regarded as recent, probably constituted by the natural satellite remains of which disintegrated after having crossed the Limite of Rock of their Planet.

Composition

The composition of the particles of the rings is variable: it is either of the Silicate S, or of frozen dust. One also finds rocks of higher size there.

Sometimes, certain rings have the moons “shepherds”: in fact small stars orbit near the edges external or in the gaps of the rings. The gravity generated by these moons maintains an edge precise with the rings. Indeed, the materials which move away from there either are returned in the ring, or ejected this one, or are integrated into the moon.

Several of the interior Jupiter moons, such Mongrel and Adrastée, are inside the annular Jupiter system, and are even beyond the limit of Rock of planet. It is possible that these rings are composed of torn off materials with these two stars by the forces of tide generated by Jupiter, perhaps helped by annular matter impacts on the surface of these bodies. A star evolving/moving beyond the limit of Rock is maintained whole only by the mechanical forces and not by its revolved: it will thus easily lose matter which will join the ring then.

The rings of Neptune are very particular because they appear since the Earth like incomplete arcs. The images transmitted by Voyager 2 showed that they were complete rings with important variations thickness. It is probably the result of the gravitational influence of the moon “shepherd” Galatée and perhaps of other still unknown similar moons.

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