. Astronomy for high schools and colleges . emembered that there is an almost infinitevariety of such shapes. The figure by Sir Jokn Herschel on the next page gives a goodidea of a spiral or ring nebula. It has a central nucleus and a smalland bright companion nebula near it. In a larger telescope thanHerschels its aspect is even more complicated. See also Fig. 128. 460 ASTRONOMY. The Omega or horseshoe nebula, so called from the resemblanceof the brightest end of it to a Greek fl, or to a horses iron shoe, isone of the most complex and remarkable of the nebulae visible inthe northern hemisphe
. Astronomy for high schools and colleges . emembered that there is an almost infinitevariety of such shapes. The figure by Sir Jokn Herschel on the next page gives a goodidea of a spiral or ring nebula. It has a central nucleus and a smalland bright companion nebula near it. In a larger telescope thanHerschels its aspect is even more complicated. See also Fig. 128. 460 ASTRONOMY. The Omega or horseshoe nebula, so called from the resemblanceof the brightest end of it to a Greek fl, or to a horses iron shoe, isone of the most complex and remarkable of the nebulae visible inthe northern hemisphere. It is particularly worthy of note, asthere is some reason to believe that it has a proper motion. Cer-tain it is that the bright star which in the figure is at the left-handupper corner of one of the squares, and on the left-hand (west)edge of the streak of nebulosity, was in the older drawings placedon the other side of this streak, or within the dark bay, thus mak-ing it at least probable that either the star or the nebula has Fig. 125.—spiral nebula. The trijid nebula, so called on account of its three brancheswhich meet near a central dark space, is a striking object, andwas suspected by Sir John Herschel to have a proper observations seem to confirm this, and in particular the threebright stars on the left-hand edge of the right-hand (east) mass arenow more deeply immersed in the nebula than they were observedto be by Herschel (1833) and Mason, of Yale College (1837). In1784, Sir William Herschel described them as in the middle ofthe [dark] triangle. This description does not apply to their^present situation. (Fig. 127). 401
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