Abstract
COMETARY REFRACTION.—M. W. Meyer, of the Observatory of Geneva, has published a discussion of three series of micrometrical observations, made during as many near approaches of the great comet of 1881 (1881 III.) to stars, when the latter were seen through the denser parts of the head of the comet, the immediate object of the micrometrical measures of distance between the nucleus and the star being the detection of any deflection or refraction of the light of the star in passing through the cojaetic nebulosity. This comet offered a great advantage in an investigation of the kind, inasmuch as its nucleus had perfectly the appearance of a fixed star. M. Gustave Cellérier had treated the question from a theoretical point of view in a memoir published in Archives des Sciences Physiques et Naturelles, of Geneva, of October 15, 1882; the conclusions are reproduced in abstract by M. Meyer, who has applied the resulting formulæ to the case in question. The first series of observations was made on June 29, 1881, when the comet passed close to the star 519 of Durchmusterung + 65°, which is No. 6594 in Oeltzen's Catalogue, of 7.8 mag. The second series, on July 13, when the comet approached the star I Draconis (Hev.) within about 38″, and the third series on August I, when it passed about 24″ from a star of 9.10 mag. For details of the method of treating the observations we must refer to M. Meyer's paper, which appears in Mémoires de læ Société de Physique et d'Histoire Naturelle de Genève, t. xxviii.; he sums up his conclusions as follows:—“La substance dont la chevelure de la grande comète de 1881 a été composée s'est optiquement comportée comme un gaz, et sa puissance réfractive à une distance de 10,200 kil. du noyau a été pendant l'époque des observations de 0.0000093. La pression de ce gaz diminuait dans les régions étudiées proportionnellement au carré de la distance au noyau.” He does not venture to say, however, that this value exactly represents the refractive power of the comet, though he believes in a measurable force.
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Our Astronomical Column . Nature 28, 158 (1883). https://doi.org/10.1038/028158a0
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DOI: https://doi.org/10.1038/028158a0