An Introduction to the Study of Spectrum Analysis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...component is of the Sirian type. Photographs taken in 1896 show that the principal component had a velocity towards the earth of 34 kilometres per second on August 31; 54 kilometres on September 16; 44 kilometres on October 5; and only 4 kilometres on November 12. The period seems to be 104 days. The pole star has been found to be a spectroscopic binary with a period of four days. Fig. 62 shows the spectra of the two components of /? Cygni--a blue star, much the brighter of the two with a spectrum similar to that of a Lyra, and a feebler companion of a yellow colour. Spectra of Comets. One of the most interesting applications of spectrum analysis in astronomy is to the determination of the nature of comets. Many hundreds of these mysterious bodies have been observed, some periodic, returning time after time; others are seen once and never seen again. From successive observations of the position of a comet, its orbit can be determined. If the orbit is a parabola, the comet is seen once when it circles round the sun, and never again; but if the orbit is an ellipse, the comet may be expected to make its reappearance after the lapse of a definite number of years. Fig. 95 shows the orbit of Halley's comet. This comet was discovered in 1682 by Halley, the Astronomer Royal of the time. He found its orbit to be an ellipse, and its periodic time to be seventy-five or seventy-six years, and therefore predicted its return in 1758; it returned punctually in 1758 and 1833, and should reappear in 1910. One of the most remarkable comets of the last fifty years was that known as Donati's comet, which was seen in 1858. The orbit of this comet is shown in Fig. 96. It attained its fullest development and greatest brilliancy in October. The tail extended 400 across...
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- 04 Jul 2012
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