Pagina's

7/21/11

Rings around the planets

Saturn is well known for its rings, but fewer people know that the other gas giants have rings as well. They are less spectacular and not visible with amateur telescopes. They were only discovered in the last decades of the twentieth century. Many of the mechanisms behind some of the ring’s properties still remain under debate. Planetary rings have always been incidental discoveries. They have fascinated and mystified for as long as we have known about them.
Jupiter
In 1979 the space probe Voyager 1 discovered the rings around Jupiter. Technically they are visible from Earth with the strongest telescopes, but they are faint and were therefore overlooked so far. The main ring is flat and about 7.000 kilometres (4.350 miles) wide and less then 30 kilometres (18 miles) thick. It is the brightest component of the ring system. Outside it lay
the two flat gossamer rings, which are much fainter and entirely made of dust. Inside the main ring lies the 20.000 kilometres (12.400 miles) thick, doughnut shaped halo.
Saturn
The ring system around Saturn is not only the most spectacular in our solar system, but also the most complex. Galileo first saw it in 1610 but did not know what it was and referred to it as “handles”. Only in 1655 the Dutch astronomer Christiaan Huygens identified it as rings with his stronger telescope. The rings are made of dust and ice particles, ranging in size from small grains to big chunks of several metres (yards) across. They even have a very thin atmosphere of oxygen. Their complicated structure is likely due to the gravitational effects of Saturn’s moons. The objects in the rings are very reflective and can therefore easily be seen, except when the rings appear edge-on.
Uranus
In 1977 astronomers discovered the rings around Uranus. This ring system is second in complexity after that of Saturn and consists of eleven separate rings. They are probably made of water ice and some organic material, which makes them very dark. Scientists believe that the rings may only be 600 million years old, very young compared to the rings of Jupiter who are believed to have formed together with the planet.
Neptune
When the Voyager 2 studied Neptune in 1989, the last known ring system of our solar system was discovered. These rings are extremely faint and dusty. There are five rings of dark, likely organic, material and a dim, unnamed ring may lay even further out. The outermost of the known rings is divided into five distinct “arcs” and is the only known planetary ring to do so.
regards from the bush
Miriam

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