File:Astronomy for the use of schools and academies (1882) (14764419415).jpg

Identifier: astronomyforuseo00gill (find matches)
Title: Astronomy for the use of schools and academies
Year: 1882 (1880s)
Authors: Gillet, J. A. (Joseph Anthony), 1837-1908 Rolfe, W. J. (William James), 1827-1910
Subjects: Astronomy
Publisher: New York : Potter, Ainsworth, & Co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ven times and a half around the earth in a second; butit would take it more than three years to reach us fromthat distance. Were all the stars blotted out of existenceto-night, it would be at least three years before we shouldmiss a single one. Alpha Centauri, the brightest star in the constellationof the Centaur, is, so far as we know, the nearest of thefixed stars. It is estimated that it would take its light aboutthree years and a half to reach us. It has also been esti- ASTRONOMY, 3^5 mated that it would take light over sixteen years to reachus from Sinus, about eighteen years to reach us from Viga,about twenty-five years from A re turns, and over forty yearsfrom the Pole-Star. In many instances it is believed thatit would take the light of stars hundreds of years to makethe journey to our earth, and in some instances even thou-sands of years. Proper Motion of the Stars. 363. Why the Stars appear Fixed.—The stars seem toretain their relative positions in the heavens from year to
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Fig. 420. year, and from age to age; and hence they have comeuniversally to be denominated as fixed. It is, however, nowwell known that the stars, instead of being really stationary,are moving at the rate of many miles a second; but theirdistance is so enormous, that, in the majority of cases, itwould be thousands of years before this rate of motionwould produce a sufficient displacement to be noticeableto the unaided eye. 366 ASTRONOMY. 364. Secular Displacement of the Stars.—Thoughproper motion of the stars is apparently slight, it will,the course of many age% produce a marked change in theconfiguration of the stars. Thus, in Fig. 420, the left-handportion shows the present configuration of the stars ofthe Great Dipper. The small arrows attached to the starsshow the direction and comparative magnitudes of theirmotion. The right-hand portion of the figure shows these

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