2011, pp 1280-1284

Planetary Rings

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Synonyms

Circumplanetary disk

Keywords

Accretion, collisions, giant planets, Jupiter, Neptune, particles, resonance, Saturn, tide, Uranus, waves

Definition

Planetary rings are systems of dust, particles, and small satellites orbiting around the giant planets of the solar system, in the nearby vicinity of a planet, where large satellites cannot form because of tidal effects.

Overview

Before observations were possible, the ancients imagined that stars were similar to the Sun and were surrounded by exoplanets, but no one imagined the possibility of planets surrounded by rings. In fact, all the giant planets are surrounded by a ring system located close to the planet. Giant planets own also large and regular satellites with prograde and circular orbits and, farther away, irregular satellites with orbits possibly retrograde and/or inclined.

The first telescope allowed Galileo Galilei to observe in 1610 that Saturn has a strange shape, which changed in course of tim ...