The Chautauquan, Vol. 05, January 1885, No. 4

by Chautauqua Literary and Scientific Circle; Chautauqua Institution

JUPITER

Makes a retrograde motion of 2° 24′ 47″, and is classed as a morning star, though he shines nearly the entire night, rising on the 1st at 9:02 p. m., and setting next morning at 10:14 a. m.; rising on the 16th at 7:59 p. m., setting on the 17th at 9:13 a. m.; and on the 30th rising at 6:56 p. m. and setting at 8:14 on the morning of the 31st. An indication that he is approaching the earth is that his diameter increased from 39.6″ on the 1st to 42.2″ on the 30th. On the 4th, at 7:24 p. m., he is 4° 2′ north of the moon.

SATURN

Has a retrograde motion of 1° 31′ 53″, and his diameter decreases during the month six-tenths of a second of arc; but this diminution affects but very slightly his brightness. As he is an evening star, the most convenient opportunities are afforded for obtaining a fine view. He rises on the 1st at 3:07 p. m., and sets on the 2nd at 5:43 a. m.; on the 15th rises at 2:04 p. m., and sets the following morning at 4:40; on the 30th, rises at 1:07 p. m., and sets on the 31st at 3:43 a. m. On the 26th, at 9:02 p. m., is 3° 27′ north of the moon.

The use of the telescope in developing the rings of Saturn is one of the interesting items in astronomical history. To one looking at this planet with the naked eye, he appears simply as a bright star; but to a person using a telescope of moderate power, he now presents some such appearance as was hinted at in the December number of The Chautauquan, and resembles a globe with an appendage on either side similar to a new moon (the concave part turned toward the globe). To the early astronomers, whose telescopes were so much inferior to ours, his appearance was a great puzzle and produced a great variety of opinions. To Galileo the planet appeared like three globes, a large one with a smaller detached one on each of two sides. To Scheiner, in 1614, he appeared as one large globe, with a small attached ball on either side. To others he appeared as a globe with crescents (shape of new moon) sometimes detached, and at other times having their cusps (sharp points) meet on the edge of the planet. And it was not until 1655 that the discovery was made that these appendages were neither balls nor crescents, but were, as then supposed, a ring (seen in various positions) around the body of the planet. In the spring of this year, Huyghens discovered that what had appeared as handles extended out on each side and were somewhat like a veritable ball with its projecting axes ready to be laid in their “bearings.” The next spring the “gudgeons” had disappeared and only the plain sphere remained. In the fall of 1656 the axes had reappeared. Thus was suggested to Huyghens that these appearances were produced by the alternate presentation to view of the edge and face of a ring, whose thickness was so small as to be invisible when its plane was directed to the eye. Being anxious to secure to himself the honor of this discovery, and yet not wishing to publish it prematurely, lest his conception should turn out to be incorrect, he printed at the end of a little pamphlet descriptive of the planet the following characters: aaaaaaa ccccc d eeeee g h iiiiiii llll mm nnnnnnnnn oooo pp q rr s ttttt uuuuu. Should his theory prove to be incorrect no one would be likely to solve the riddle; should it be correct, as it proved to be, he readily arranged the letters to read: Annulo cingitur tenui, plano nusquam cohaerente, ad eclipticam inclinato; which being translated means: “Girdled by a thin, plane ring, nowhere touching, inclined to the ecliptic.” It was soon ascertained that the ring had an inclination of 27° to the plane of its orbit, and as it with the planet revolves about the sun, its axis maintains the same absolute position; so that as the revolution is made once in every twenty-nine and a half years, every fourteen and three-fourth years its edge is directly toward the sun, and, practically, toward the earth (since the distance of the earth from the sun is comparatively small), and is invisible except through the most powerful telescopes. In like manner, every fourteen and three-fourth years the greatest possible portion of the ring’s surface is presented to the sun, and if the ring were perpendicular to the plane of the earth’s orbit, and its axis directed toward the earth, we should see the globe entirely girdled, instead of seeing, as we do, a large portion of one side of the ring and the opening only on two sides between it and the planet.

After Huyghens, the discovery was made by an English astronomer named Ball, that instead of only one ring, Saturn had two rings, divided by a narrow, dark line, and that the inner ring was broader than the outer in about the ratio of seventeen to ten; that is, the breadth of the inner was estimated to be 17,000 miles, while that of the outer was only 10,300 miles. In 1850, Prof. Bond, of Cambridge, discovered a third ring lying between the inner ring and the planet. But this was hardly regarded as a discovery, as this ring had been “seen in England by Messrs. Lassell and Dawes, before it was formally announced by the Bonds;” and “something of the same kind had been seen by Dr. Galle, at Berlin, as far back as 1838.”

Another perplexing question is, whether there are changes going on in these rings, and if so, what they are. Struve, in 1851, propounded the theory that the inner edge of the ring (or rings) was gradually contracting, and thus lessening the space between it and the planet, and this at the rate of about 1.3″ per century; at which rate it would close in on the planet about the year 2150—a date at such a distance that the event, should it transpire, will be of little moment to our readers.

Another not yet satisfactorily answered question is, of what are these rings composed? The generally accepted answer at present is, that it is neither a solid nor a fluid ring, but a cloud of satellites, too small and too numerous to be seen singly. “They are like the separate little drops of water out of which are composed fogs and clouds, which, to our eyes, seem like solid masses.”

URANUS

Reaches his stationary point on the 6th, at 5:00 p. m., having made a direct motion of 51.45″; during the rest of the month he retrogrades 17′ 12.6″. On the 6th, at 6:50 p. m., he is 1° 18′ north of the moon. He figures as a morning star, rising on Dec. 31st, ’84, at 11:29 p. m., and setting on New Year’s at 11:25 a. m.; on the 15th, rising at 10:30 p. m., and setting on the 16th at 10:26 a. m.; on the 29th, rising at 9:33 p. m., and setting on the 30th at 9:31 a. m.