Stars and telescopes; a hand-book of popular astronomy founded on the 9th ed. of Lynn's Celestial motions (1901)
Todd, David P. (David Peck), 1855-1939, Lynn, William Thynne, 1835-1911 · Boston, Little, Brown · leaf 338
re called spectroscopicbinaries; for their periods are not reckoned in years, but in The Fixed Star. 285 are found to be endowed with regular though slowchanges of place in the heavens, called their proper days, or even hours. If the orbit of a close binary is seenedge on, twice in every revolution… … ALVAN GRAHAM CLARK (1S32-1S97) critical points: in the first pair, the lines appear sharplysingle; in the second pair, they are found to be double. Thissingular phenomenon is readily explained by Dopplers im-portant and most useful principle (page 56), according towhich the lines in the spectrum of…
Astronomy
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