Thus all the visible stars in the firmament have been arranged into ninety-four constellations, of which forty-eight were formed by the ancients, and the rest within the last two or three hundred years. Of the stars above enumerated, there are about 17 of the first magnitude, 76 of the second, 223 of the third, and the remainder of the fourth, fifth, and sixth magnitudes. The different classes of magnitudes are intended to express their apparent brightness. The brightest stars are said to be of the first magnitude; those which appear next in brightness, or inferior to the first, are classed in the second magnitude; and so on down to the sixth magnitude, which comprises the smallest stars visible to the naked eye in the clearest night; though there are but few eyes that can distinguish those which belong to the sixth magnitude. All the stars beyond these limits come under the general denomination of Telescopic stars; and with the most powerful telescopes, stars may be perceived of all classes, from the sixth to the sixteenth order of magnitudes. Every increase in the power of these instruments brings into view innumerable multitudes of those orbs which were before invisible, so that no definite limits can be assigned to the apparent brightness or magnitudes of the stars This classification into magnitudes, however, as it is entirely arbitrary, so it is extremely indefinite, and can convey no very accurate ideas even of their apparent brightness or intensity of light. This consideration has led some eminent astronomers to endeavour to estimate the apparent brightness of each star by experiments made with the photometer. From various experimental comparisons of this kind, the late Sir Wm. Herschel deduced the following conclusions: Light of a star of the average 1st magnitude = 100 2d 3d 4th 5th 25 12 2 So that the light of a star of the second magnitude is one fourth of that of a star of the first magnitude; the light of one of the third, one eighth; of the fourth, one sixteenth; of the fifth, one fiftieth; and of the sixth, only one hundredth part. Sir John Herschel informs us that, from his own experiments, he has found that the light of Sirius, the brightest of all the fixed stars, is about 324 times that of an average star of the sixth magnitude. It may be proper to observe that the stars specified in the statements inserted above are not all visible to the naked eye, nearly two thirds of them being perceptible only by the tele D scope; but they are those stars whose latitudes and longitudes, and whose right ascensions and declinations, have been accurately determined. They form only a very small proportion of those which are found to exist in the most distant regions of the firmament; for by powerful telescopes there have been explored in a single speck of the heavens a number which far exceeds that of all the visible stars in the sky; and catalogues have been formed in modern times which comprise from fifty to a hundred thousand of these luminaries. The first astronomer, so far as we know, who attempted to make a catalogue of the stars, was Hipparchus of Rhodes, who flourished about 120 years before Christ. Having observed a new star which he had never seen before, he began to doubt whether there might not be changes occasionally taking place among these luminaries, and therefore commenced making a catalogue of them, noting down the position and magnitude of each star, with the view that, if any new star should again appear, or any of those observed by him should increase or be diminished in magnitude, or totally disappear, such changes might be known to those who should live in future ages. This catalogue, which was handed down to us by Ptolemy, an ancient Egyptian astronomer, has been of special use to modern astronomers, both in determining the rate of the precession of the equinoxes, and in proving that certain stars which then existed are no longer to be seen in the heavens; thus indicating that changes and revolutions are taking place among the distant bodies of the universe. The catalogue of Hipparchus contained a description of the places of 1026 stars. The Arabians are the next whom history represents as having attempted to form a descriptive catalogue of the stars. This was effected by Ulug Beigh, the grandson of Timurlane, from his own observations made at Samarcand, whose catalogue contains 1022 stars. Tycho Brahe, the celebrated Danish astronomer, who lived in the sixteenth century, by means of the large and accurate instruments he invented, formed a catalogue of 777 stars, which are considered as superior in correctness to those of Hipparchus and Ulug Beigh. He was prompted to this laborious undertaking by the sudden appearance of a new star in Cassiopeia, in the year 1572, which shone with the brilliancy of Venus, and was visible even at noonday. Bayer soon after published a catalogue of 1160 stars, in which he introduced the practice of distinguishing the stars by the letters of the Greek alphabet. All the catalogues now mentioned were formed before the telescope was invented, and contained nearly all the stars which could be perceived by the unassisted eye. Soon after the invention of the telescope, in the beginning of the seventeenth century, the celebrated Hevelius composed a catalogue of 1888 stars, of which 1553 were observed by himself, and their places computed for the year 1660. But some of our modern observers of the heavens have published catalogues which contain the positions of many thousands of stars, besides multitudes of nebulæ, of various descriptions, double, triple, and quadruple stars, and various other celestial phenomena. The division of the heavens into constellations, and the names and figures by which they are distinguished, seem to have been of a very ancient date. Job, who is supposed to have lived in a period prior to that of Moses, refers to some of them by the same names which they still bear. "Canst thou bind the sweet influences of Pleiades"—or the seven stars" or loose the bands of Orion?" that is, the belt of Orion, which consists of three equidistant stars in a straight line. "Canst thou bring forth Mazzaroth in his season? or canst thou guide Arcturus with his sons?" Arcturus is a bright star of the first magnitude in the constellation of Bootes, and is here put for the constellation, itself. The expression "his sons" is supposed to refer to Asterion and Chara, the two Greyhounds, with which he seems to be pursuing the Great Bear around the North Pole in the diurnal revolution of the heavens. Mazzaroth is generally supposed to refer to the twelve signs of the zodiac, which, by their appointed revolutions, produce the succession of day and night, and the seasons of the year. In another part of this book, Job, when filled with profound reverence of the majesty of God, declares that He alone "spreadeth out the heavens, and maketh Arcturus, Orion, and the Chambers of the South." The prophet Amos, who lived 800 years before the Christian era, alludes to the same objects in the fifth chapter of his prophecy : "Ye who turn judgment to wormwood, and leave off righteousness in the earth, seek Him who maketh the seven stars and Orion, who turneth the shadow of death into the morning, and maketh the day dark with night; that calleth for the waters of the sea, and poureth them out upon the face of the earth: the Lord of Hosts is his name.' |