Studies of the Nebulae: Made at the Lick Observatory, University of California, at Mount Hamilton, California, and Santiago, Chile, Volume 13

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University of California Press, 1918 - 268 pages

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Page 12 - Andromeda situated five hundred times as far away as at present, it would appear as a structureless oval 0(2 long, with very bright center, and not to be distinguished from the thousands of very small round or oval nebulae found wherever spirals are found. There is an unbroken progression from such minute objects up to the great Nebula in Andromeda itself. I see no reason to believe that these very small nebulae are of a different type from their larger neighbors."2 This argument is a daring extrapolation...
Page 48 - ... any lack of symmetry, such asymmetry is almost invariably with reference to the major axis of the ellipse. This asymmetry manifests itself frequently in 'lanes' prominent on one side of the major axis and faint or invisible on the other, in a fan-shaped nuclear portion, in an apparent displacement of the nebular material on one side of the major axis, or in various combinations of these effects. Fifteen elongated nebulae show prominent dark lanes on one side of the major axis. Contributory evidence...
Page 12 - ... planetaries and diffuse galactic nebulosities and the objects, spirals and others, that swarm in regions of high galactic latitude. Curtis has expressed this new point of view by dividing nebulae into three classes — planetaries, diffuse, and spirals.1 In explanation of the term "spiral...
Page 170 - Fig. 69. Curve of velocities and frequencies. Let v be the observed radial velocity of a nebula situated at angular distance d from the solar apex, and let v0 be the velocity of the solar system with reference to the system of observed nebulae.
Page 17 - C, would appear to be the only reason for changing the larger estimates, and this evidence is only to be secured by taking many additional plates at random. In conclusion, I see no reason, at present existing, for changing the estimate made in this paper, that at least 700,000 small spirals are within reach of large reflecting telescopes.
Page 45 - It has long been a matter of common knowledge that certain spiral nebulae seen edgewise show a dark lane running down the length of the spiral, an appearance generally explained as due to a band of absorbing or occulting matter.
Page 17 - II* 22™ + 17° 46' 69 12* i5™ 4- 6° i' 81 12" 55m + 28° 30' 304 56? his estimate would have been increased by at least 60 per cent. (he found 864 new nebulae in all, and the larger plates he used would have added a number to those counted on the Crossley plates). Perhaps all the reasons outlined above may be regarded as contributing to an explanation of the difference between Path's estimate of 162,000, and the larger ones due to Perrine and the present investigation. Of these, the possibility...
Page 256 - ... classification. It has its maximum, according to Miss Cannon, in Class Oe stars. It has been assigned by various observers to as many elements, but the best case seems to have been made out by Lockyer, Baxendall and Butler who identify it with a line of abnormal behavior in the spectrum of nitrogen.2 Whatever its chemical source its strength in Class O stars argues for its common origin in these and in the nebulae. A line which plays an equally, or perhaps more, important part in stars a little...
Page 256 - ... laboratory determination made with a highly rarefied tube containing a gaseous hydrocarbon compound. A faint nebular line has been photographed in this vicinity by several observers, but only rough determinations of its position have been published. The mean of five of my measures places it at 4267. 28A. The line is very faint and this value may be in error, say 0.2 of an angstrom. The South Kensington observers have found' the carbon line 4267.30 to be accompanied by a doublet in position 4647.53,...
Page 14 - ... owing to the distance from the optical axis, that only the brighter of the small nebulae can be picked up in these outer parts of the plate. The greater proportion of the small nebulae are found in the more central parts having an area of six tenths of a square degree, or less. I have assumed 0.75 of a square degree as the average effective area on which the counts were made; this is certainly somewhat in excess, but is an error on the conservative side. We shall first assume that these 439 regions...

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