Abstract
SOME months have now elapsed since an announcement by Mr. Hind informed astronomers that a well-known telescopic comet, first seen in the years 1772 and 1805, and rediscovered in 1826 by the astronomer Biela, of Josephstadt, in Bohemia, when it was first recognised as periodic, would make its nearest approach to the earth towards the close of this year; and its apparent place on successive nights was duly foretold, to assist them in their search for its existence. On the last two occasions of its expected returns, in 1859 and 1866, no signs of the missing comet were detected. The favourable circumstances under which it was expected to be observed, during its last approach to the earth in 1869, and the absence of any notice of its having been seen during the last two months of its anticipated reappearance in the present year, makes it hardly doubtful that, as an interesting study and examination with the most powerful modern telescopes, it has at length ceased to be any longer visible. When at its greatest brightness in the year 1805, it was seen by Olbers, with the naked eye, and in its subsequent returns, it was frequently attentively observed with the most powerful means and by the most expert astronomers. During its appearance in 1846 it was first distinctly perceived to separate into two portions, gradually receding from each other until they gained a greatest distance, which was estimated on that occasion at 157,000 miles. The two portions remained visible as two distinct comets at their next return in 1852, with a widened interval between them, which had increased to 1,250,000 miles. With nearly equal brightness, and with perfect cometary appearance, these two bodies travelled side by side, and journeyed together, doubtless, to separate still further from each other in their further circulations round the sun. Such is the telescopic history of Biela's comet. In the year 1818 a telescopic comet was discovered by Pons, the astronomer, at Marseilles, whose date of appearance, at least a year before the time of a punctual return, cannot have been a reappearance of Biela's comet, but the position of its orbit, as far as it could be calculated from the imperfect data that were obtained, are so similar to that of Biela's that its relation to that comet appears not improbably to be of the same kind as that which formerly connected together the two portions of the recently divided cometary pair, and the orbit and periodic time of this third comet probably differ but little from those of the principal comet from which it may fairly be presumed to have been derived. Such groupings of comets on nearly parallel courses appear to be distinguishable in the more remarkable cases, recently pointed out by Hoek, of some comets with hyperbolic orbits; and the revolution of more than one telescopic comet is thought to have been discovered in the same orbit with the periodically-returning comet of 1866, with which the meteor-current of the great November star-shower, at its recent return, was shown by Schiaparelli, Adams, and Oppolzer, to be in remarkable agreement. In a later letter to the Times, in August last, Mr. Hind pointed out the satisfactory coincidence of which Prof. Schiaparelli, the former coadjutor of Secchi, and now the able director of the Observatory at Milan, was the first discoverer, between the orbit of another comet of considerable brightness seen in 1862, and the course of the meteors of the well-known August star-shower, an unusually bright display of which was recorded shortly after the appearance of that comet in the following year. Another example of distinct resemblance between the orbit of a meteor current and that of a periodic comet was early discovered by the German astronomers Drs. Weiss and Galle in the case of the meteor shower of April 19–20 and the comet I, 1861, to which Prof. Kirkwood, of the State University in Indiana, U.S., has lately added the interesting observation that the earliest records of this meteor shower, as well as of a conspicuous star-shower annually visible about October 18–20, indicate a periodic time in their maximum returns, which corresponds, like that of the November meteor system and its attendant comets, to an ellipse whose major axis is very nearly the mean distance of the planet Uranus from the sun. The time has thus arrived when systematic observations of meteor showers may be regarded as an important auxiliary to astronomers in certain cases where the orbits of comets are intersected by the earth's path, by vying with the telescope in detecting the hidden courses of such comets as, by comminution or disbanding of their substance, have so lost their brightness, as at length completely to elude their search.
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HERSCHEL, A. The Cometary Star-Shower . Nature 7, 77–78 (1872). https://doi.org/10.1038/007077a0
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DOI: https://doi.org/10.1038/007077a0