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next fifteen it appears to drop below the apparent center of the planet; and while shifting from one extreme to the other, the rings become almost invisible, appearing only as a faint line of light running from the planet in opposite directions. The rings vary also in their inclination, sometimes dipping to the right, and at others to the left.
TELESCOPIC PHASES OF THE RINGS OF SATURN.
The above is a good representation of the various inclinations and degrees of expansion of the rings of Saturn, during his periodic journey of 30 years
501. The rings of the planet are always directed more or less toward the Earth, and sometimes exactly toward us; so that we never see them perpendicularly, but always either exactly edgewise, or obliquely, as shown in the last figure. Were either pole of the planet exactly toward us, we should then have a perpendicular view of the rings, as shown in the adjoining cut.
502. The various phases of Saturn's rings are explained by the facts that his axis remains parallel to itself (see following cut), with an uniform inclination to the plane of his orbit, which is very near the ecliptic; and as the rings revolve over his equator, and at right angles with his axis, they also remain parallel to themselves. The revolution of the planet about the Earth every 30 years, must therefore bring first one side of the rings to view, and then the other-causing all the variations of expansion, position, and inclination which the rings present.
501. How are the rings situated with respect to the Earth? How would they appear if either pole of Saturn were toward us? 502. How are the various phases of Saturn's rings accounted for?
BATURN AT DIFFERENT POINTS IN HIS ORBIT.
Here observe, first, that the axis of Saturn, like those of all the other planets, remains permanent, or parallel with itself; and as the rings are in the plane of his equator, and at right angles with his axis, they also must remain parallel to themselves, whatever position the planet may occupy in its orbit.
This being the case, it is obvious that while the planet is passing from A to E, the Sun will shine upon the under or south side of the rings; and while he passes from E to A again, upon the upper or north side; and as it requires about 30 years for the planet to traverse these two semicircles, it is plain that the alternate day and night on the rings will be 15 years each.
A and E are the equinoctial, and C and G the solstitial points in the orbit of Saturn. At A and E the rings are edgewise toward the Sun, and also toward the Earth, provided Saturn is in opposition to the Sun. To an observer on the Earth, the rings will seem to expand from A to C, and to contract from 0 to E. So, also, from E to G, and from G to A. Again: from A to E the front of the rings will appear above the planet's center, and from E to A below it.
The rings of Saturn were invisible, as rings, from the 22d of April, 1848, to the 19th of January, 1849. He came to his equinox September 7, 1848; from which time to February, 1856, his rings will continue to expand. From that time to June, 1868, they will contract, when he will reach his other equinox at E, and the rings will be invisible. From June, 1863, to September, 1870, they will again expand; and from September, 1870, to March, 1877, they will contract, when he will be at the equinox passed September 7, 1848, or 29 years before.
The writer has often seen the rings of Saturn in different stages of expansion, and contraction, and once when they were almost directly edgewise toward the Earth. At that time (January, 1849), they appeared as a bright line of light, as represented at A and E, in the first cut on the preceding page.
503. The dimensions of the rings of Saturn may be stated in round numbers as follows:
Distance from the body of the planet to the first
508. State the distances and dimensions of his rings, beginning at the body of the planet, and passing outward? What additional statistics from Herschel?
In a recent work, entitled "The New Theory of Creation and Deluge," it is predicted that, at some future time, the fluid rings of Saturn may descend and deluge the planet, as ours was deluged in the days of Noah. Sir David Brewster says:-" Mr. Otto Struve and Mr. Bond have lately studied with the great Munich telescope at the Observatory of Pulkoway, the third ring of Saturn, which Mr. Dassels and Mr. Bond discovered to be fluid. These astronomers are of opinion that this fluid ring is not of very recent formation, and that it is not subject to rapid change, and they have come to the extraordinary conclusion that the inner border of the ring has, since the time of Huygens, been gradually approaching the body of Saturn, and that we may expect, sooner or later, perhaps in some dozen of years, to see the rings united with the body of the planet." 504. The rings of Saturn serve as reflectors to reflect the light of the Sun upon his disc, as our Moon reflects the light to the Earth. In his nocturnal sky, they must appear like two gorgeous arches of light, bright as the full moon, and spanning the whole heavens like a stupendous rainbow.
In the annexed cut, the beholder is supposed to be situated some 30° north of the equator of Saturn, and looking directly south. The shadow of the planet is seen travelling up the arch as the night advances, while a New Moon is shown in the west, and a Full Moon in the east at the same time.
505. The two rings united are nearly 13 times as wide as the diameter of the Moon; and the nearest is only th as far from the planet as the Moon is from us.
The two rings united are 27,500 miles wide; which+2160 the moon's diameter=127. So 240,000 miles, the Moon's distance 19,000 the distance of Saturn's interior ring=1213.
At the distance of only 19,000 miles, our Moon would appear some forty times as large as she does at her present distance. How magnificent and inconceivably grand, then, must these vast rings appear, with a thousand times the Moon's magnitude, and only one-twelfth part of her distance!
506. The periodic time of Saturn being nearly thirty years, his motion eastward among the stars must be very slow, amounting to only 12° a year, or one sign in 2 years. It will be easy, therefore, having once ascertained his position, to watch his slow progress eastward year after year. Saturn is now (1855) just east of the seven stars.
MOONS OF SATURN.
507. Besides the magnificent rings already described, the telescope reveals eight satellites or moons, revolving around Saturn. But these are seen only with good instruments, and under favorable circumstances.
504. What purpose do the rings of Saturn serve? How appear in his evening sky! 505. Width of two rings, as compared with Moon? Distance? Demonstrate both. How would our Moon appear at the distance of Saturn's rings? 506. Eastward motion of Saturn? How traced? 507. Moons of Saturn? How seen? Best time for observing?
SATELLITES OF SATURN.
The best time for observing them is when the planet is at his equinoxes, and his rings are nearly invisible.
In January, 1849, the author saw five
of these satellites, as represented in the adjoining cut. The rings appeared only as a line of light extending each way from the planet, and the satellites were in the direction of the line, at different distances, as here represented
508. These satellites all revolve eastward with the rings of the planet, in orbits nearly circular, and, with the exception of the eighth, in the plane of the rings. Their mean distances, respectively, from the planet's center are from 123,000 to 2,366,000 miles; and their periods from 22 hours to 79 days, according to their distances.
The distances and periods of the satellites of Saturn are as follows:
Of the 8th satellite recently discovered, we have as yet much less knowledge than of its predecessors.
COMPARATIVE DISTANCES OF THE MOONS OF SATURN.
12 3 4 5
509. The most distant of these satellites is the largest, sup posed to be about the size of Mars; and the remainder grow smaller as they are nearer the primary. They are seldom eclipsed, on account of the great inclination of their orbits to the ecliptic, except twice in thirty years, when the rings are edgewise toward the Sun. The eighth satellite, which has been studied more than all the rest, is known to revolve once upon its axis during every periodic revolution; from which it is inferred that they all revolve on their respective axis in the same manner.
Let the line A B represent the plane of the planet's orbit, C D his axis, and EF the plane of his rings. The satellites being in the plane of the rings will revolve around the shadow of the primary, instead of passing through it, and being eclipsed.
At the time of his equinoxes, however, when the rings are turned toward the Sun (see A and E, cut, page 242) they must be in the center of the shadow on
SYSTEM OF SATURN-NO ECLIPSES.
508. The revolutions? Shape and position of their orbits? Distances from their pri mary? 509. Comparative size?
the opposite side; and the moons, revolving in the plane of the rings, must pass through the shadow at every revolution. The eighth, however, may sometimes escape, on account of his departure from the plane of the rings, as shown in the cut.
510. The theory of the satellites of Saturn is less perfect than than that of the satellites of Jupiter. The difficulty of observing their eclipses, and of measuring their elongations from their primary, have prevented astronomers from determining, with their usual precision, their mean distances and revolutions. But of this we are certain: there is no planet in the solar system, whose firmament presents such a variety of splendid and mag. nificent objects as that of Saturn.
The various aspects of the seven moons, one rising above the horizon, while another is setting, and a third approaching to the meridian; one entering into an eclipse, and another emerging from one; one appearing as a crescent, and another with a gibbous phase; and sometimes the whole of them shining in the same hemisphere, in one bright assemblage! The majestic motion of the rings-at one time illuminating the sky with their splendor, and eclipsing the stars; at another, casting a deep shade over certain regions of the planet, and unveiling to view the wonders of the starry firmament, are scenes worthy of the majesty of the Divine Being to unfold, and of rational creatures to contemplate.
Such displays of Wisdom and Omnipotence, lead us to conclude that the numerous splendid objects connected with this planet, were not created merely to shed their luster on naked rocks and barren sands; but that an immense population of intelligent beings is placed in those regions, to enjoy the bounty, and adore the goodness, of their great Creator.
PRIMARY PLANETS.-URANUS AND NEPTUNE.
511. URANUS is the next planet in order from the Sun, beyond or above Saturn. To the naked eye, it appears like a star of only the 6th or 7th magnitude, and of a pale, bluish white; but it can seldom be seen, except in a very fine, clear night, and in the absence of the Moon. Through a telescope, he exhibits a small, round, uniformly illuminated disc, without rings, belts, or discernible spots. His apparent diameter is about 4", from which he never varies much, owing to the smallness of our orbit in comparison with his own.
510. Is the system of Saturn well understood? Why not? Of what are we sure? What scenes must it present? To what conclusion must these phenomena lead us! 511. Position and appearance of Uranus? Through a telescope?