Ring (astronomy)

“ The ring is differently presented to the sun, one part being nearer than the other, the nearer part being attracted more forcibly. If we take the point in the ring nearest the sun where there is the greatest attraction, and draw a line to the opposite point where the attraction is least, we can show that the case stands in this way: the sun's pull may be analysed into two forces, one of them represented by the line joining the centre of the sun and the centre of the ring, and another at right angles 125 to it let fall from the point most strongly attracted on to the first line. ”

“ When we see the Ring most open, it’s shadow upon the Planet is broadest; and from that time the shadow grows narrower, as the Ring appears to do to us; until, by Saturn’s annual motion, the Sun comes to the plane of the Ring, or even with it’s edge; which being then directed towards us, becomes invisible on account of it’s thinness; as shall be explained more largely in the tenth Chapter, and illustrated by a figure. The Ring disappears twice in every annual Revolution of Saturn, namely, when he is in the 19th degree both of Pisces and of Virgo. ”

“ If a model about a foot in diameter were cut out of tissue paper, the relative proportion of size and thickness would be about right. In space the thickness is very nearly 100 miles, so that, when we look at the ring system edge-on, it becomes all but invisible except in very large telescopes. Clearly a ring so thin cannot be a continuous solid object and recent observations have proved beyond a doubt that Saturn's rings are made up of millions of separate particles moving round the planet, each as if it were an individual satellite. ”

“ The reader who cares enough about such subjects to take the necessary trouble, can easily make a little model of Saturn and his ring system, which will very prettily illustrate the effect of the rings both in reflecting light to the planet's darkened hemisphere and in cutting off light from the planet's illuminated hemisphere. Take a ball, say an ordinary hand-ball, and pierce it through the centre with a fine knitting-needle. Cut out a flat ring of card, proportioned to the ball as the ring system of Saturn to his ball. ”

“ No one could suppose that a ring for a planet could be formed within the body of the nebula and abandoned, or thrown out, afterwards, because centrifugal force could not throw out the ring and at the same time retain the surrounding matter. ”

“ The Milky Way itself is commonly thought to be a ring, or series of rings, like the coils of the great spiral nebula in Andromeda, and separated from us by a space far greater than the thickness of the ring itself. ”

“ Even this complicated arrangement, however, would not save the ring-system. If we suppose a fine hoop to turn around a central attracting body as the rings of Saturn rotate around the planet, it may be shown that unless the hoop is so weighted that its centre of gravity is far from the [Pg 200] planet, there will be no stability in the resulting motions; the hoop will before long be made to rotate eccentrically, and eventually be brought into destructive collision with the central planet. ”

“ When examined with a high power the edges of the ring have a fringed appearance, and numerous glittering stellar points become visible both within and without its circumference. This nebulous ring, though a small object in the telescope, is of enormous magnitude, and if it were not more distant than 61 Cygni, one of the nearest of the fixed stars, its diameter would not be less than 20,000 millions of miles, but it has been estimated by Herschel that it is 900 times more remote than Sirius. ”

“ The present time, when Saturn is the ruling planet of the night, seems favourable for giving a brief account of recent speculations respecting the Saturnian ring-system, especially as the observations of Mr. Trouvelot appear to remove all doubt as to the true nature of the rings, if indeed any doubt could reasonably be entertained after the investigations made by European and American astronomers when the dark inner ring had but recently been recognised. ”

“ It was "conformable,"—that is, its track produced backward passed through the common radiant—and it was undoubtedly a member of the August group. The observations were discussed by Professor H. A. Newton, of Yale College, who deduced from them the following approximate elements of the ring:8
The earth moving at the rate of 68,000 miles per hour, is at least five days in passing entirely through the ring. ”

“ The rings were constantly in motion, in their orbit around Saturn. And each body in the rings had its own private motion in respect to the others. Some gyrated fantastically around others.
A huge body might in turn exert enough gravitation of its own to hold smaller bodies in its grip, and force them to become its "moons." And these satellites then perturbed nearby bodies, causing them to weave and shuttle within the ring.
In short, any body in the ring might shift position enough in the space of a minute or two to be lost forever.
Timkin shot back to the coal lump. ”

“ Such a ring doubtless had a diameter of some million miles; we readily perceive that the particles of matter in the outer part of the belt would have a swifter movement around the sun than those on the inside. When by some disturbance, as possibly by the passage of a great meteoric body of a considerable gravitative power, this ring was broken in two, the particles composing it on either side would, because of their mutual attraction, tend to draw away from the breach, widening that gap until the matter of the broken ring was aggregated into a sphere of the star dust or vapour. ”

“ Their rate of progress is gradually reduced as they approach together, and they begin to expand and enlarge, but they never touch each other. Another peculiar feature about the rings consists in the fact, that the central core of air in the ring remains the same all the time the ring is in motion through the room, so that it has the same core of air at the end of its journey as it had when it left the box. ”

“ Leading scientists wrote technical letters demonstrating not only that the Ring could not possibly be controlled in space when beyond the earth's attraction, but that it was manifestly absurd to suppose that it could even get away from the earth's attraction at all. One distinguished pedagog was particularly insistent upon the point that the gravitational force of the earth was a sina qua non for steering the Ring in a given direction. ”

“ During the present century, other observers have detected more divisions of the ring, one separating the outer ring into two rings of equal breadth seems to be permanent. It is to be seen only by the best telescopes, under the most favorable conditions. ”

“ The rings are then exhibited in their full beauty. The divisions, the dark ring, and the strange shading of the middle ring, can be well seen in a telescope of adequate power. The telescopic view is still more interesting when (as in fig. 30) the planet throws a well-marked shadow upon the rings.
But perhaps the most beautiful of all the features which Saturn presents to the telescopist is the strange variety of colour to be observed upon his surface, and upon that of the rings. ”

“ Thus turning, it divided into successively formed rings, each of which in time broke up, the matter of the ring gathering into a separate planet. At first this planet, like the original mass, was gaslike, and when separated from the sun it began to gather in on itself, in most cases forming rings, which in time were to alter into the lesser spheres—the moons. The earth and all the planets lying further away from the sun have these little bodies about them, but in one case, as if to show the stages of creation, the unbroken ring remains, forming the magnificent circles which girdle Saturn. ”

“ At the inner edge of the inner ring begins that strange structure called the crape ring, which extends halfway towards the globe of the planet. The most remarkable point about the crape ring is its semi-transparency, for we can sometimes see the globe of the planet through this strange curtain. The crape ring can only be observed with a powerful telescope. ”

“ The rings of Saturn stretched like a level sheet in all directions, though actually composed of millions of tiny bodies. Homer Timkin carefully braked with the nose rockets till he floated motionlessly with respect to the ring's own rotary motion around its primary. Then he eagerly donned his vac-suit.
Had he struck it rich this time? Through his binoculars, a moment ago, he had seen the glint of one small jagged lump among the ring debris—and it had glinted like gold or silver. There was vast treasure among the rings, if one could find it.... ”

“ There can be no doubt that any attempt to depict the rings of Saturn only represents the salient features of that marvellous system. We are situated at such a great distance that all objects not of colossal dimensions are invisible. We have, indeed, only an outline, which makes us wish to be able to fill in the details. We long, for instance, to see the actual texture of the rings, and to learn of what materials they are made; we wish to comprehend the strange and filmy crape ring, so unlike any other object known to us in the heavens. ”

“ Webb states that when the ring system was at its greatest breadth he has seen it [pg 182] with a power of about twenty on only 11⁄3-inch aperture. A beginner cannot expect to do so much with such small means; but at all events a 2-inch telescope with powers of from 50 to 100 will reveal the main outlines of the ring very well indeed, and, with careful attention will show the shadow of the ring upon the ball, and that of the ball upon the ring. When we come to the question of the division in the ring, we are on somewhat more doubtful ground. ”

“ Looking at these singular companions of the planet across a gulf eight or nine hundred millions of miles wide, it is not surprising that an astronomer prays for "light, more light," to resolve this puzzle of the bright and the dark. It is only an outline of the ring, at the best, that we can expect to obtain from the most careful drawings. But what Herschel did not suspect or imagine about the ring, it would be natural for him to confound with, other features that took a greater hold of his fancy. ”

“ When the ring appears like a very narrow ellipse, a short time previous to its disappearance, the division, or dark space between the rings, cannot be seen by ordinary instruments.
Sir W. Herschel very properly observes, ‘There is not perhaps another object in the heavens that presents us with such a variety of extraordinary phenomena as the planet Saturn; a magnificent globe, encompassed by a stupendous double ring; attended by seven satellites; ornamented with equatorial belts; compressed at the poles; turning upon its axis; mutually eclipsing its ring and satellites, and eclipsed by them ”

“ An ancient method of divining by the ring is similar in principle to the modern table-rapping. The edge of a round table was marked with the characters of the alphabet, and the ring stopped over certain letters, which, being joined together, composed the answer.
In another method of practising Dactylomancy, rings were put on the finger-nails when the sun entered Leo, and the moon Gemini, or the sun and Mercury were in Gemini and the moon in Cancer; or the sun in Sagittarius, the moon in Scorpio, and Mercury in Leo. ”

“ Planetary rings were formed of the gems assigned to the several planets, each set in its appropriate metal: thus, the Sun, diamond or sapphire in a ring of gold; the Moon, crystal in silver; Mercury, magnet, in quicksilver; Venus, amethyst in copper; Mars, emerald in iron; Jupiter, cornelian in tin; Saturn, turquoise in lead.
From the remotest antiquity every planet in the heavens was believed to possess a virtue peculiar to itself. Each presided over some kingdom, nation, or city ”

“ But in 1850 came the last great addition to our knowledge of the ring [pg 178] system, W. C. Bond in America, and Dawes in England making independently the discovery of the faint third ring, known as the Crape Ring, which lies between the inner bright ring and the globe.
The extraordinary appendages thus gradually revealed present a constantly varying aspect according to the seasons of the long Saturnian year. At Saturn's equinoxes they disappear, being turned edgewise; then, reappearing, they gradually broaden until at the solstice, 71⁄3 years later, they are seen at their widest expansion ”