Optical surface features and morphologic properties of the Orion Nebula
In the field partsH, K, L andM of the Orion Nebula, indicated in Figure 2, no obvious differences do appear in the monochromatic photographs obtained in Hα+[Nii], [Oii], the visual continuum and the range of the Balmer continuum. A different situation we meet in the rest of the field, where one observes two types of featuresA andB, distinguished in Figure 1 by solid and dashed bordering lines respectively. Relative to the conditions in the Hα+[Nii] pictures, the typeA areas gain in intensity in the photographs taken in the visual continuum. the emission in the forbidden [Oii] lines at λ 3727 Å is correlated with Hα+[Nii], the emission in the range of the Balmer continuum with the visual continuum. According to these properties theA-areas must have a particularly high percentage of scattered star light.
Most of the areas with identical monochromatic features show a high deficiency of cluster stars correlated with a low surface brightnesss and a reduced gas density. This is explained by an opaqueness of the emission strata in the direction in the line of sight and a position of the same nearer to the observer than the extension of the cluster. There appear surface structures at large distances from the Trapezium which show a correlation between the intensity of scattered star light and the intensity of the emission of the higher ions ([Oiii], [Neiii]). This observation is considered as a proof that ‘canals’ through the nebular cloud complex allow in some directions the exciting radiation to reach large distances from the star without having suffered an appreciable absorption or scattering.
KeywordsRadiation Large Distance Surface Structure Surface Feature Morphologic Property
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