“Silver planet both of eve and morn,”
and by Plato the same fact is recognized. The other planets, all of which had, according to him, been originally named in Egypt and Syria, have each its descriptive title in his nomenclature. Thus the innermost, “the Star of Mercury,” is called Stilbon, “the Sparkler,” Mars, Pyroeis, “the Fiery One,” while Jupiter, the planet of the slowest course but one, is designated as Phaeton, and Saturn, the tardiest of all, Phaenon. These names were in later times abandoned in favor of those of the divinities to whom they were respectively dedicated, unalterably associated now with the days of the week, over which they have been selected to preside.
The Copernican theory, which once and forever “brushed the cobwebs out of the sky,” by clearing away the mists of pre-existing error, first completely explained the varying positions of the Shepherd’s star, irradiating the first or last watch of night, according to her alternate function as the follower or precursor of the sun. As she travels on a path nearer to him by more than twenty-five and a half million miles than that of the earth, she is seen by us on each side of him in turn after passing behind or in front of him. The points at which her orbit expands most widely to our eyes—an effect of course entirely due to perspective, as her distance from the sun is not then actually increased—are called her eastern and western elongations; that at which she passes by the sun on the hither side her inferior, and on the farther side her superior conjunction. At both conjunctions she is lost to our view, since she accompanies the sun so closely as to be lost in his beams, rising and setting at the same time, and travelling with him in his path through the heavens during the day. When at inferior conjunction, or between us and the sun, she turns her dark hemisphere to us like the new moon, and would consequently be invisible in any case, but when in the opposite position, shows us her illuminated face, and is literally a day star, invisible only because effaced by the solar splendor. It is as she gradually separates from him, after leaving this latter position, circling over that half of her orbit which lies to the east of him, that she begins to come into view as an evening star, following him at a greater and greater distance, and consequently setting later, until she attains her greatest eastern elongation, divided from the sun about 45 deg. of his visible circuit through the heavens, and consequently remaining above the horizon for some four hours after him. From this point she again appears to draw nearer to him until she passes on his hither side in inferior conjunction, from which she emerges on the opposite side to the westward, and begins to shine as a morning star, preceding him on his track, at a gradually increasing distance, until attaining her greatest westward elongation, and finally completing her cycle by returning to superior conjunction once more in a period of about five hundred and eighty-four days.