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TOPIC: Uranus


L

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Uranus blue ring
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Uranus's recently discovered outermost ring is bright blue.

The blue ring is associated with the small moon Mab.
Saturn also has a blue outer ring.

"The outer ring of Saturn is blue and has Enceladus right smack at its brightest spot, and Uranus is strikingly similar, with its blue ring right on top of Mab's orbit" - Imke de Pater, professor of astronomy at the University of California at Berkeley.

Uranus has eleven rings. These rings are made of large rocks up to 10 meters wide.
The other rings are a reddish colour due to them being composed of larger particles that reflect red light, or they contain iron. The blue colour may also be the result of absorption of red light by methane.

The colour of Saturn's blue ring is due to small particles ejected into space by Enceladus as it orbits around the planet. But the same probably isn't true for Uranus.
Uranus' newly discovered moon, Mab, is a small, dead, rocky ball only about 24 kilometres across ó one-twentieth the diameter of Enceladus.
However, scientists suspect that both of these rings are subject to forces acting on dust in the rings, which allow the tiny particles to survive while the larger ones are captured by their moons.
These fragments are subject to forces that push them away or toward the planet out of the moon's orbit. The result is a ring of small particles, each only a fraction of a human hair in width, that reflect and scatter mostly blue light.


This schematic view shows the outer rings of Saturn (top) and Uranus (bottom), with each ring system scaled to a common planetary radius.

"This model can be transferred directly to what we now see in Uranus. Although we still need to understand the details of the process" - Imke de Pater

The study is detailed in Friday's issue of the journal Science.

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RE: Uranus
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-- Edited by Blobrana at 21:36, 2005-12-22

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The new outer ring is twice the diameter of the planetís previously known ring system.

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Uranus Rings
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Astronomer Mark Showalter, using the Hubble Space Telescope have discovered two more rings around Uranus.
This is the first such discovery since the Voyager 2 spacecraft flew past the planet 20 years ago, in 1986 and discovered the 10th and 11th thin ring arcs.
The other nine rings were discovered from Earth.

The new rings orbit within the orbits of its large moons and just outside of Uranus' previously known 11 known rings. The newly discovered rings are made up of short-lived, faint bands of dust grains that are constantly being replenished by erosion of the orbiting moons. The moon Mab, that was discovered in 2003 restocks the outermost ring.
Scientists made the latest ring discoveries in 2004 after reprocessing hundreds of images taken by Voyager and found the rings had been imaged in the pictures. The rings were overlooked during the spacecraft flyby because of their faintness.

Astronomers have measured changes in the orbits of Uranus' inner moons since 1994. New measurements suggest the moons are in a "random and chaotic" fashion
Because of the moons' instability, scientists think the satellites will lead to a collide with one another in the next couple of million years.

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Uranus
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