Abstract
COMET SWIFT (α 1892).—At the Boyden Station, Arequipa, Peru, during the visibility of this comet, all the photographic telescopes were turned towards it, with the result that a fine series of photographs were obtained. In the Bache 8-inch photographic doublet, fifty-six pictures (20 millimetres to the degree) were taken, sixteen of which “are of the first quality” ;in the 2˙5-inch photographic doublet (3˙8 millimetres to the degree) twelve satisfactory plates were taken, while in the 13-inch refractor and 20-inch reflector several additional negatives were collected. An examination of the negatives, especially of those belonging to the first series, indicated two important facts, as Mr. A. E. Douglass (Astronomy and Astrophysics for March) informs us. (1) That the tail of the comet was composed of luminous masses receding from the head at a measurable rate, and (2) that the form of the tail depended largely on some varying torce acting at the head. The former of these results was deduced from measurements of the distance of prominent points (8 points were here used) from the nucleus, and the acceleration he obtained amounted to 477,000 miles per day. In discussing the second fundamental results, he deals with the general characteristics of the tail and the special phenomena within half a degree of the head, separately. The tail he describes as “a bundle of slightly divergent straight streamers, branching from each other and joined to the head by one, two, or three well-marked lines.” At the southern part of the tail the photographs showed the appearance of a curious twisting effect, while a number of faint streamers, in many cases not joined to the main part of the tail, were also visible. The curve of the natural tangents of the position angles for the date on which they left the head, is, as plotted out by Mr. Douglass, quite irregular, and suggests “non-periodic outbursts from the head of the comet or variations in the repulsive force of the sun”; where the tail swings to one side there are “large jets in the opposite direction as if the whole resulted from some increase in activity in the head.” He suggests that this activity may be connected with solar disturbances, just as magnetic storms on the earth may be connected with certain classes of sunspots.
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Our Astronomical Column. Nature 47, 546–547 (1893). https://doi.org/10.1038/047546a0
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DOI: https://doi.org/10.1038/047546a0