Jupiter

A remarkable result of the Voyager spacecraft's encounter with Jupiter was the discovery of a ring of particles orbiting Jupiter. This ring is much smaller and simpler than the familiar rings of Saturn, and they are not visible directly from Earth. Since their discovery, however, astronomers have made measurements of them by watching the light from stars as they pass behind the rings. In this way they can measure their extent and density.

The rings extends to approximately 1.7 Jovian radii from the center of the planet. Small "shepherd" moons The four largest satellites of Jupiter are the Galilean satellites, named after seventeenth century Italian astronomer Galileo who was the first to observe them with a telescope and describe them as moons. This composite image shows the four satellites to scale: Europa (upper left), Callisto (upper right), Io (lower left), and Ganymede (lower right). All but Europa are larger than our moon. Ganymede is larger than Mercury. U.S. National Aeronautics and Space Administration (NASA). (Metis and Adrastea) may act to help gravitationally confine the ring material, creating a sharp outer boundary. Indeed, debris lost from these shepard satellites is thought to be the ring's origin. The rings are about 3,728 mi (6,000 km) wide and about 19 mi (30 km) thick. They are dark and there is some internal band structure to the rings. The size of material is very small, a few microns in size (like fine dust).