File:Astronomy for the use of schools and academies (1882) (14764090352).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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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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Fig. 421. stars as they will appear thirty-six thousand years from thepresent time. Fig. 421 shows in a similar way the present configura-tion and proper motion of the stars of Cassiopeia, andalso these stars as they will appear thirty-six thousand yearshence. Fig. 422 shows the same for the constellation Orion. 365. The Secular Motion of the Sun. — The stars in allparts of the heavens are found to move in all directionsand with all sorts of velocities. When, however, the motions ASTRONOMY. & of the stars are averaged, there is found to be an apparentproper motion common to all the stars. The stars in the

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