Comet-tail structures in emission nebulae.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Comet-tail structures in emission nebulae. Osterbrock, Donald E. Abstract A catalogue is given of a large number of "comet-tail" or "elephant-trunk" structures in several emission nebulae whose distances are known from spectroscopic parallaxes. The dimensions of the comet-tail structures and the orlentations of their axes with respect to directions to the 0 stars exciting the nebulae are listed. The statistics of these dimensions show that the forms of these structures are in general agreement with the theory of their origin presented by van de Hulst, Spitzer, Frieman, Layzer, and others. The observational evidence suggests that in the final stages of development their tips become larger in diameter than their necks, and eventually break off, forming separate droplets. Several different observations show that the densities in the bright ionized rims of the comet-tail structures are considerably higher than the densities in the main bodies of the emission nebulae to which they belong. Finally, the application of these structures to the galactic structure problems of locating distant 0 stars and of deter mining the distances of Hii regions is discussed. Mount Wilson and Palomar Observatories, Carnegie Institution of Washington, Calofornia Institute of Technology, Pasadena, Calof. Publication: The Astronomical Journal Pub Date: 1957 DOI: 10.1086/107652 Bibcode: 1957AJ.....62S..28O full text sources ADS |