Sunday, July 29, 2012

4 Planets Have Rings in Solar System

Jupiter, Saturn, Uranus, and Neptune all have rings. Jupiter's rings were discovered by the interplanetary space probe Voyager 1 in March 1979. The rings extend 80,240 miles (129,130 kilometers) from the center of the planet. They are about 4,300 miles (7,000 kilometers) wide and less than 20 miles (30 kilometers) thick. A faint inner ring is believed to extend to the edge of Jupiter's atmosphere.
Saturn has the largest, most spectacular set of rings in the solar system. Saturn's rings were first recognized by Dutch astronomer Christiaan Huygens (1629-1695) in 1659 and were examined in detail by the Voyager I and Voyager 2 missions in 1980 and 1981. Saturn's rings are about 41,168 miles (66,400 kilometers) wide and 169,800 miles (273,200 kilometers) in diameter, but less than 10 miles (16 kilometers) thick. There are six different rings, the largest of which appears to be divided into thousands of ringlets. The rings appear to be composed mainly of frozen water—in the form of snowflakes, snowballs, hailstones, and icebergs—ranging in size from 3 inches to more than 10 yards in diameter.
In 1977, when Uranus occulted (passed in front of) a star, scientists observed that the light from the star flickered or winked several times before the planet totally blocked the star from view. The same flickering occurred as Uranus continued on its path and the star came back into view. The reason for this flickering was determined to be the presence of rings around Uranus. Nine rings were initially identified and Voyager 2 discovered two more in 1986, bringing the total to eleven. The rings are thin, narrow, and very dark.
Voyager 2 also discovered a series of at least five very faint rings around Neptune in 1989. The rings are made up of particles, some of which are greater than one mile in diameter and are considered "moonlets." Where these particles clump together, they create relatively bright areas called "arcs."

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