Astronomy in a nutshell, the chief facts and principles explained in popular language for the general reader and for schools (1912)
Serviss, Garrett Putman, 1851-1929, Rouben Mamoulian Collection (Library of Congress) DLC · New York, London, G.P. Putnam's sons · leaf 178
small. It has been found thatthey occur in periods, averaging about elevenyears from maximum to minimum, althoughthe length of the period is very irregular.It has also been observed that when the firstspots of a new period appear, they aregenerally seen some 30° from the equator,either toward the… … Tress Nebula (N. G. C. 6992) in Cygnus Photographed at the Yerkes Observatory by G. W.Ritchey, with the two-foot reflector.Observe the strangely twisted look of this long curved nebula ; also thecurious curves composed of minute stars near it. THe Svin 133 or the other. The duration of…
Astronomy
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