Abstract
The discovery on 1977 March 10 of the Uranian rings caused enormous interest amongst researchers. Indeed, the origin and stability of narrow elliptical rings turned out to be very problematic. First of all, a narrow ring must spread out because of the exchange of angular momentum between colliding particles — after a number of centuries, with a characteristic “viscous” time t v ~ (vk 2)−1 — increasing its width and diminishing the steepness of its edges. Secondly, the asphericity of the Uranian field causes a precession of elliptical orbits at a rate which depends on the major semi-axis. The difference in the precession of particles at the outer and the inner edges of the ring — differential precession — must after a few hundred years separate the lines of apsides of the particles, destroy an elliptical narrow ring and form a circular, wider ring. Nonetheless, the rings have not spread out and have clearly defined boundaries, and precess as a whole.
“... You are always badgering me about my ring; but you have never bothered me about the other things that I got on my journey.”
“No, but I had to badger you” said Gandalf. “I wanted the truth. It was important. Magic rings are — well, magical; and they are rare and curious. I was professionally interested in your ring, you may say; and I still am.”
J.R.R. Tolkien, The Lord of the Rings.
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© 1999 Springer-Verlag Berlin Heidelberg
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Fridman, A.M., Gorkavyi, N.N. (1999). Resonance Effects in Planetary Rings II Narrow Ringlets and Satellites. In: Physics of Planetary Rings. Astronomy and Astrophysics Library. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-03918-2_10
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DOI: https://doi.org/10.1007/978-3-662-03918-2_10
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-08437-9
Online ISBN: 978-3-662-03918-2
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