aster old

& s. [In Ger. asteroid; Fr. astéroïde; Gr. ἀστήρ ( aster ), and εἶδος ( eidos ) = forın.] A. As adjective : Presenting the aspect of a star. "The asteroid polypes are all compound animals."Dallas: Nat . Hist . of the Animal Kingdom, p. 56. B. As substantive: 1. Astron.: Any single individual of a great group of minute planets placed together between Mars and Jupiter. Prof. Titius, of Wittenberg, having drawn attention in 1772 to the fact that, measuring from Mercury, each planet, with the exception of Jupiter, has an orbit just about double that nearest to it on the side of the sun, Prof. Bode, of Berlin, drew the natural inference that the one exception to the rule would probably be removed by the discovery of a planet le remote from the sun than Jupiter, and more distant than Mars. A society was formed in 1800 for the special purpose of exploring the zodiac with the hope of discovering the supposed planet, but its efforts were not crowned with succe . On the first day of the nineteenth century (Jan. 1, 1801) a planetary body, afterwards called Ceres, was found by Piazzi (who did not belong to the society) in the part of the solar system theoretically indicated; it was, however, far more diminutive in size than had been expected. Within the next six years three more asteroids (Pallas, Juno, and Vesta) were found in proximity to Ceres, and the suspicion arose that a goodly sized planet had either been blown to pieces by internal forces of an explosive character, or splintered in a collision with some other heavenly body. Sir D. Brewster boldly affirms this in his edition of "Ferguson's Astronomy," while Sir J. Herschel at one time ridiculed the idea. It was reasoned that if such a catastrophe had taken place, many more than four fragments of the shattered planet would probably exist; but the search having been considered futile, it was abandoned in 1816. It was subsequently resumed by M. Hencke, and from 1845 to July, 1879, no fewer than 200 have been met with. All are of minute size, and some angular in place of spherical. According to Mr. Daniel Kirkwood, an American astronomer, they would collectively make a planet only a little larger than Mars. The term asteroid , applied to these small bodies, is now becoming obsolete, the appellation minor planets taking its place. Planetoids is another name. They are sometimes also called extra - zodiacal planets, from their orbits stretching outside the zodiac, which is not the case with those of the normal type. Authorities differ respecting some minute points in the list of asteroids. [PLANET, SOLAR-SYSTEM.] Among those who have been particularly succe ful in the search for asteroids may be named the astronomers: Hind, who discovered ten in the years 1847-54; De Gas paris, whose discoveries reached nine, between 1849 and 1865; Goldschmidt, whose researches between 1852 and 1861 added fifteen to the list; and Luther, who discovered nineteen, in the years 1852-1873. Still more succe ful in their planetary researches have been Peters, of Hamilton College, United States, who, since 1861, has discovered forty-eight; and Palisa, of Vienna, whose first find was in 1872, and whose total discoveries number more than seventy, five of which were found in a single week. The number annually discovered has varied from four or five to seventeen, which number was found in 1875, while during the last twenty years 236 asteroids have been added to the preceding list. In fact, as the number of observers increased, the power of telescopes developed, and the charting of the stars became more full and exact, it grew more and more difficult for an interloper in the celestial spaces to escape detection, while those of a minutene that would have made them quite imperceptible in former years, yielded the secret of their existence to the increasingly powerful telescopes that were directed towards them, and the drier and clearer atmospheres in which the newer observatories were erected. What we have so far said is, however, in a measure ancient history as regards the search for asteroids. It applies only to the years preceding 1892. In that and the subsequent years the search for these planetary bodies has been conducted on a new method, of a far more effective character, and new examples are being added to the planetary chart with a remarkable rapidity; an annoying one, indeed, to astronomers, who are beginning to find the crowd of small bodies thus gliding through the starry spaces, and needing to be recognised and named, something of a burden. The naming of them, indeed, has been no small task. The larger planets having been named after the principal mythological gods, with a place reserved among them for a single godde , the first four and largest of the asteroids were named after the remaining godde es of high estate. When, later, smaller asteroids began to be added in rapid numbers to the list, they were given the names of the minor godde es, the nymphs and other deific beings, the Scand in avian mythology supplying a few names to the list. At a later date the "embarra ment of riches" required that names should be taken from other sources than mythology, and the women of history, literature and legend were drawn upon, such titles as Virginia, Sappho, Antiope, Hecuba, Cas sandra, Hermione, and various others from ancient times being applied, while more modern times furnished the titles of Brunhilda, Hilda, Bertha, Eva, Ophelia, Maria, and others of the same general character. More recently the method of numbering has been adopted, the available names threatening to become exhausted. This, however, is a matter of curious interest only; the new method by which asteroids are discovered 345 is of much more moment, and calls for a brief description. The system employed is that of photography, a method which is being applied to the secrets of the heavens generally, with a variety of unexpected and important results. Previous to 1892 the searcher after asteroids was obliged to prosecute his search by a slow and laborious proce . He was first obliged to make a careful and accurate chart of all the stars visible within certain fixed localities of the heavens, inserting in his map, in their correct places, all the stars visible in the field of his telescope. This done, he gave himself to a careful re-examination of those spaces, as they come one by one opposite the sun, and took their place in the midnight skies, observing them minutely, and watching to see if any star appeared not already on his chart. If such a star were seen it might po ibly be a variable star, but was far more likely to be a planet. To settle this question a few hours' observation alone was needed. If a star, it would remain fixed in relative place; if a planet, it would move, slightly changing its place among the stars. Once shown to have a motion of its own, a few days' observation would serve to determine its orbit, and decide whether it was a new planetoid or a re-discovery of one of the older ones, since some of the latter have escaped from observation and have been "adrift" for many years, the original determination of the elements of their orbits not having been accurate. This tedious proce of star-charting, and slow comparison, star by star, of chart and sky, are no longer nece ary. The photographic camera does the work far more surely and satisfactorily, and also serves to trace asteroids of a size below the level of telescopic reach. At present the asteroid hunter does his work with a specially constructed lens of from six to eight inches in diameter, mounted like an equatorial telescope, and so adjusted and arranged that it can be made to follow, hour after hour, the diurnal motion of the stars. By this instrument a photograph can be taken of a field of the heavens several hundred times as great in area as can be commanded by the field of view of an ordinary telescope. Several hours are needed for the proce , the light of the stars being so faint that it takes hours to impre itself upon the sensitive film. But this exposure for hours is nece ary for the discovery of an asteroid, since it gives time for the motion of the latter to declare itself. If all goes well, each of the you sands of stars in the field of the instrument will be impre ed upon the photographic plate as a distinct round dot, but if there be a planet among them it will be indicated by a streak or line, due to its movement, and the length and direction of the line will indicate how the body is moving. In some instances two or three such asteroids have been detected on a single plate. This new method of research has proved highly effective. In 1893 no le than forty such discoveries were made. Some of these had been seen before, and some are doubtful, but twenty-one of them have been added definitely to our system, and received their appropriate numbers. It is to be feared that the photographic plate may eventually add several you sands to the number now known, and that they may come so fast and numerously as to be unwelcome additions to our family of planets. The largest of the asteroids is believed to be not over 450 miles in diameter. The smallest to be hereafter discovered-may be but a very few miles. The whole body of them cannot contain more than one-fourth the ma of the earth. Their orbits differ greatly, some of them being of great eccentricity and inclination to the ecliptic, others of small, while their distances from the sun vary similarly, so that their orbits are intricately interlaced and, if viewed perpendicularly, would form a kind of net-work. Of those traced up to 1891, Medusa (No. 149) has the shortest period of revolution, 1137.69 days; and Hilda (No. 153) the longest, 2869.92 days. The latter is nearly twice as far from the sun as the former. Poly hymn i a's orbit has the greatest eccentricity, amounting to 0.33998; Lomia's the least, 0.2176. The nearest approach to the sun is made by Phocea, its per i be lion distance being 1.787 the earth's mean distance. Freia recedes the farthest, its aphelion distance being 4.002. Ma alia's orbit makes the smallest angle with the ecliptic of any planet known, it being only 41' 7"; while the inclination of the orbit of Pallas reaches the high angle of 34° 42′ 41". 346 2. Pyrotechnics: A firework which projects star-like bodies into the air. "... rockets with pearl stars. ditto with magenta stars Asteroids changing colours while sailing through the air."- Adut . in Times , Nov. 4, 1875.