Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 598
Irregular Nebulae. — There are many nebulae inthe sky of enormous extent and irregular form. Among thefinest examples of these objects, though by no means themost extensive, are the veil-like structures which are seen inthe constellation Cygnus, one of which is shown in Fig. 187.It is altogether… … Fig. 187. — Irregular nebula in Cygnus (N. G. C. 6960). Photographed byRitchey with the two-foot reflector of the Yerkes Observatory. 552 AN rNTRODUCTION TO ASTRONOMY [ch. xiii, 301 certainly a hundred years are required for light to cross them.They are extremely faint (the long-exposure…
Astronomy
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