Studies of the Nebulae: Made at the Lick Observatory, University of California, at Mount Hamilton, California, and Santiago, Chile, Volume 13University of California Press, 1918 - 268 pages |
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Page 77
... nebular lines in the same spectra to their normal , or zero - velocity wave- lengths . Knowing their normal wave - lengths , the observed wave - lengths of the same lines in the spectrum of any nebula could be converted into the ...
... nebular lines in the same spectra to their normal , or zero - velocity wave- lengths . Knowing their normal wave - lengths , the observed wave - lengths of the same lines in the spectrum of any nebula could be converted into the ...
Page 79
... lines on the photographs the 3 - prism combination reduced the exposure times to about one - fifth that required by the 1 - prism combination . In effect , this permitted the inclusion of a relatively large number of faint nebulae in ...
... lines on the photographs the 3 - prism combination reduced the exposure times to about one - fifth that required by the 1 - prism combination . In effect , this permitted the inclusion of a relatively large number of faint nebulae in ...
Page 80
... nebular lines are correspondingly long . In these cases only the helium comparison spectrum was impressed upon the plates , as the hydrogen Hẞ comparison line would have fallen upon the nebular Hẞ line , and thus have rendered both lines ...
... nebular lines are correspondingly long . In these cases only the helium comparison spectrum was impressed upon the plates , as the hydrogen Hẞ comparison line would have fallen upon the nebular Hẞ line , and thus have rendered both lines ...
Page 81
... of the objects must remain in some doubt , and spectro- grams of them obtained under different conditions will give varying results ; and there seems to be no gain in accuracy as to the velocities VELOCITIES OF THE BRIGHT - LINE NEBULAE 81.
... of the objects must remain in some doubt , and spectro- grams of them obtained under different conditions will give varying results ; and there seems to be no gain in accuracy as to the velocities VELOCITIES OF THE BRIGHT - LINE NEBULAE 81.
Page 82
... nebular lines are much under - exposed , and the probable errors increase in consequence . The probable errors of the southern hemisphere observations are in general appreciably larger than those of the Mount Hamilton observations . We ...
... nebular lines are much under - exposed , and the probable errors increase in consequence . The probable errors of the southern hemisphere observations are in general appreciably larger than those of the Mount Hamilton observations . We ...
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Studies of the Nebulae: Made at the Lick Observatory, University ..., Volume 13 Lick Observatory,Joseph Haines Moore Affichage du livre entier - 1918 |
Expressions et termes fréquents
absorption appears bright bands bright lines brighter center at Aa central star continuous spectrum dark line DETAILS OF OBSERVATION diameter diffuse nebulosity disk Dispersion Measurer Lines edge effect elongated exposure faint fainter figure g slitless Greater Magellanic Cloud H N₁ N₂ hydrogen hydrogen lines inclination km./sec lane Lick Obs LICK OBSERVATORY long Hẞ M. T. Exp major axis minor axis Miss Hobe N Miss Hobe N₁ moderately bright Moore Miss Hobe Moore N Moore N₁ N₂ N₁ N₂ Hẞ N₂ HB N₂ Hẞ Hy nearly round nucleus band object Orion nebula photographic planetary nebulae radial velocity region relative intensities relative velocity ring Ring Nebula rotation s.n. Planetary Scott N₁ Sept Slit long small nebulae spectra spectrograms spiral nebulae star of magn stellar condensations stellar nucleus ultra-violet under-exposed wave-lengths whorls Wilson N₁ Wolf-Rayet Wolf-Rayet stars Ηβ Ηγ
Fréquemment cités
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...