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Uranus Rings and Two Moons


Voyager 2 has discovered two "shepherd" satellites associated with the

rings of Uranus. The two moons -- designated 1986U7 and 1986U8 -- are

seen here on either side of the bright epsilon ring; all nine of the

known Uranian rings are visible. The image was taken Jan. 21, 1986,

at a distance of 4.1 million kilometers (2.5 million miles) and

resolution of about 36 km (22 mi). The image was processed to enhance

narrow features. The epsilon ring appears surrounded by a dark halo

as a result of this processing; occasional blips seen on the ring are

also artifacts. Lying inward from the epsilon ring are the delta,

gamma and eta rings; then the beta and alpha rings; and finally the

barely visible 4, 5 and 6 rings. The rings have been studied since

their discovery in 1977, through observations of how they diminish the

light of stars they pass in front of. This image is the first direct

observation of all nine rings in reflected sunlight. They range in

width from about 1OO km (6O mi) at the widest part of the epsilon ring

to only a few kilometers for most of the others. The discovery of the

two ring moons 1986U7 and 1986U8 is a major advance in our

understanding of the structure of the Uranian rings and is in good

agreement with theoretical predictions of how these narrow rings are

kept from spreading out. Based on likely surface brightness

properties, the moons are of roughly 2O- and 3O-km diameter,

respectively. The Voyager project is managed for NASA by the Jet

Propulsion Laboratory.


credit: NASA/JPL

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Taken on May 16, 2012