The Adolfo Stahl lectures in astronomy, delivered in San Francisco, California, in 1916-17 and 1917-18, under the auspices of the Astronomical Society of the Pacific (1919)
Astronomical Society of the Pacific, Aitken, Robert Grant, 1864-1951 · San Francisco Stanford University Press · leaf 167
uta theory as yet, perhaps the most acceptable hypothesis, becauseof their high speeds and small numbers, is that the planetarynebulae are to be regarded as a somewhat sporadic case instellar evolution, arising through some collision or cataclysm,and not to be regarded as cases typical of the… … Fig. 1—.-^t left, region in the Milky Way showing ten to twenty thousand stars,one planetary (N. G. C. 6563), and no spirals. Fig. 2—At right, region near N. G. C. 2507, some distance from the Milky Way,showing few stars and tifty-thrce small nebulae, indicated by rings. Thearea of eacli lialf is…
Astronomy
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