Astronomy for amateurs . itobliquely, and it appears to us elliptical; a part of thering seems to pass in front of Saturn, and its shadowis visible on the planet, while the opposite part passesbehind. This ring, which measures 284,000 kilometers(176,080 miles) in diameter, and less than 100 kilometers(62 miles) in breadth, is divided into three distinct zones:the exterior is less luminous than the center, which isalways brighter than the planet itself; the interior isvery dark, and spreads out like a dusky and faintlytransparent veil, through which Saturn can be distin-guished. What is the nat
Astronomy for amateurs . itobliquely, and it appears to us elliptical; a part of thering seems to pass in front of Saturn, and its shadowis visible on the planet, while the opposite part passesbehind. This ring, which measures 284,000 kilometers(176,080 miles) in diameter, and less than 100 kilometers(62 miles) in breadth, is divided into three distinct zones:the exterior is less luminous than the center, which isalways brighter than the planet itself; the interior isvery dark, and spreads out like a dusky and faintlytransparent veil, through which Saturn can be distin-guished. What is the nature of these vast concentric circlesthat surround the planet with a luminous halo ? They 160 THE PLANETS are composed of an innumerable number of particles,of a quantity of cosmic fragments, which are swept offin a rapid revolution, and gravitate round the planetat variable speed and distance. The nearer particlesmust accomplish their revolution in 5 hours, 50 minutes,and the most distant in about 12 hours, 5 minutes, to. Fig. 48.—Varying perspective of Saturns Rings, as seenfrom the Earth. prevent them from being merged in the surface of Saturn:their own centrifugal force sustains them in space. With a good glass the effect of these rings is moststriking, and one can not refrain from emotion on con-templating this marvel, whereby one of the brothers ofour terrestrial country is crowned with a golden diadem. 161 ASTRONOMY FOR AMATEURS Its aspects vary with its perspective relative to the Earth,as may be seen from the subjoined figure (Fig. 48). We must not quit the Saturnian province w^ithoutmentioning the eight sateUites that form his splendidsuite: Names. Distance from the planet. Time of revolution. Kilometers. ]\Iiles. Days. Hours. Minutes. 1. Mimas 207,000 128,340 22 37 2. Enceladus 257,600 159,712 i 8 53 3. Tethys 328,800 203,856 i 21 18 4. Dione 421,200 261,144 ^ ^7 4^ 5. Rhea 588,400 364,808 4 12 25 6. Titan 1,364,000 845,680 15 22 41 7. Hyperion 1,650,000 1,023,000 2
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