STAR

(Yunanca köken — orijinale bakınız.) In a popular sense, the term star is used to designate any celestial body whatever, including the planets; but in astronomy it is applied only to those self-shining bodies which are situated beyond the sphere of solar attraction, and consequently do not par ticipate in the motions of the solar system. One of the first results of the observation of the li'iivms was, that the stars maintain always the same positions relatively to each other. Hence they were called./!] in distinction to the planets, or wandering stars, which are constantly changing their places in the armament The fixity of the stars is, indeed, not absolute; lor modem observations have detected some changes of relative position among them; but these changes are so minute, that, in gen era], they only become sensible after the lapse of a number of years, by a comparison of positions determined with the most perfect instruments at the beginning and end of the interval. They are consequently altogether inappreciable to una isted vision, and the discovery of their existence lias not rendered a change of language nece ary: astronomers still speak of the fixed stars. Apparent Magnitude of the Stars. — The first circum Stance which arrests the attention of the observer of the stars is the great differences of their apparent magnitudes or their relative brightne . In order to establish a gradation in this respect, and for the convenience of description and reference, astronomers divide them into cla es or orders, which are called magnitudes. A few of the most brilliant are denominated stars of the first magnitude; those of an inferior degree of brightne aie of the second magnitude; and so on down to the Oth or 7th, which, according to the established convention, romprehund all the stars visible to the naked eye. The gradation is, however, still continued among those which are only visible in the telescope, and magnitudes from the 8lb to the 16th are familiar to those who are in the practice of using powerful instruments. It is, however, to be remarked, that this cla ification is not based on any photemetrical determination, but is entirely arbitrary. "Of a multitude of bright objects," says Sir John Herschel, "differing, probably, intrinsically, both in size and splendour, and arranged at unequal distances from us, one must of nece ity appear the brightest, one next below it,and so on. An order of succe ion must exist; and it is a matter of absolute Indifference where, in thai infinite progre ion downward* from the brightest to the invisible, we choose to draw our lines of demarcation. All this is matter of pure convention. Usage has, however, established such a convention; and although it is impo ible to determine exactly, or a prior i, where one magnitude ends and another begins, and although different observers have differed in their magnitudes, yet, on the whole, astronomers have restricted their first magnitudes to about 15 or 90 principal stars, their second to 50 or 00 next inferior, their third to about 200 yet smaller, and so on; the numbers increasing very rapidly as we descend in the scale of brightne , the whole number of stars already registered, down to the 7th magnitude inclusive, amounting to 15,000 or 20,000." (Astronomy, Cabinet Cyclopaedia, p. 371.) Arrangement and Nomenclature of the Stars. — In order to indicate the quarter of the heavens in which any star is situated, astronomers, in the earliest ages of the science, had recourse to the method of forming them into groups, to which they gave the name of constellations, or aeterianu (see Constellation), and distinguished the different groups one from another by appellations borrowed in general from mythology, and suggested by vague resemblances or fanciful analogies, the origin of which it is now difficult or impo ible to trace. A few of the brightest stars received particular names; some of which, conferred by the Creeks and Arabs, have been preserved, as Sirius, Rigel, Aldebaran, Arcturus, Capella, .; but it is obvious that this nomen clature could not be carried to any great extent. The system which has prevailed in modern times, and been generally adopted by astronomers in their charts and catalogues, was invented by Bayer, whose Uranometria, containing charts of all the constellations, was first published at A ugs burg in1603. It consists in distinguishing the stars belonging to each constellation by the letters of the alphabet, beginning with the brightest, which is called a. The next brightest is called /?, the next in order of brightne y, and so on; and when the letters of the Greek alphabet were exhausted, Bayer had recourse to the Roman, and then to the Italian. It is to be observed, that the order of the letters indicates only the relative brightne of stars in the same constellation, without reference to other parts of the heavens. Admitting the principle, it might have been sim pier to have employed the ordinal numbers 1, 2, 3, 4, , for distinguishing individual stars. But great perplexity 5s caused by the irregular forms of the constellations, whose numerous contortions•and inter lacings with each1151other baffle [s. 1165]