Abstract
THE DENSITY OF SATURN's RING.—M. Poincaré supplies a short note on the stability of Saturn's ring in the November number of the Bulletin Astronomique. Laplace had shown that the ring could only be stable if it were divided into several concentric rings revolving at different speeds. M. Tisserand had confirmed this result, and had recognised that a single ring must, in order to exist, possess much higher density than the planet, and had calculated the maximum breadth of each elementary ring in terms of its density and mean radius. M. Poincaré has carried this investigation a step further, and shown that if the density of a ring be less than a certain amount, will, under the influence of the slightest perturbation, no longer break up into a number of narrower rings, but into a great number of satellites, and that if the rings be fluid and turn each as a single piece, the density of the inner ring must be at least , and of the outer ring 1/16 that of the planet. For a ring of very small satellites (not for a fluid-ring, as M. Poincaré erroneously states), Maxwell has shown the condition to be that the density should not exceed 1/300 part of that of Saturn.
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Our Astronomical Column . Nature 33, 303–304 (1886). https://doi.org/10.1038/033303a0
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DOI: https://doi.org/10.1038/033303a0