Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The structure of the network nebulae. Chamberlain, Joseph W. Abstract The intensity variations in the eastern part of the network nebulae in Cygnus (N.G.'C. 6992 and 6995) are treated by the method of turbulence analysis. The quantity F(k) is derived following the procedure of Aller.1 Here F(k) dk is a measure of the intensity fluctuation contained in segments of the nebulosity with wave numbers between k and k + dk, ir7k being the diameter of a segment. The plate analyzed was made with the new H. D. Curtis Schmidt camera on Eastman ~o~a-E emulsion with a red plexiglass filter. This plate and filter effectively isolate Hot. Very little difference was found between the F(k) `s derived for the intensity, I, and for the square root of the intensity. Three regions in the nebulae were traced with a microphotometer and subsequently analyzed. In all three regions F(k) shows a sharp peak at about ir/k = 4 or 5 minutes of arc, which is about the size, as measured on the plate, of the largest and brightest segments of nebulosity and distinct groups of fine filaments. Towards large values of k, F(k) falls off roughly as k-2. An attempt to interpret F(k) as a true turbulence spectrum analyzed from the point of view of density fluctuations meets with some difficulties. The turbulence in these nebulae, if indeed turbulence is the cause of the intensity fluctuations, is probably neither homogeneous nor isotropic. Thus'the situation differs from that in the Cygnus region recently photographed at Palomar and discussed by Aller.1 Also, the intensity of Hot may not be proportional to the square of the nebular density, since excitational forces other than stellar illumination may be present in these nebulae. These forces could conceivably cause the level of ionization to vary with position. An attempt is currently being made to derive the dependence of the Balmer emission on the electron density and temperature on the hypothesis, made by Oort, that the excitational energy arises from the impact of an expanding nova shell colliding with an interstellar gas cloud. I.Ap. J., 113, 120, 1951. Observatory, University of Michigan, Ann Arbor, Mich. Publication: The Astronomical Journal Pub Date: April 1951 DOI: 10.1086/106592 Bibcode: 1951AJ.....56Q.123C full text sources ADS |

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