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J. O. Kane, D. D. Ryutov, B.A. Remington, S. G. Glendinning (Lawrence Livermore National Laboratory), Marc Pound (University of Maryland), David Arnett (University of Arizona)
The towering ‘Pillars of Creation’ of the Eagle Nebula are a long-standing astrophysical mystery. A new initiative is underway to develop a model for the formation of the Pillars, employing three-dimensional numerical modeling and scaled verification experiments using intense lasers. In the Rayleigh-Taylor instability (RT) model of the Pillars advanced almost fifty years ago by Spitzer and Frieman (Spitzer, L. 1954, ApJ 120, 1; Frieman, E. A. 1954, ApJ 120, 18), radiation from nearby stars photo-evaporates and accelerates the cloud surface, and the Pillars are falling ‘spikes’ of dense gas. Recently, fluid velocities and column densities in the Pillars have been measured (Pound, M. W. 1998, ApJ 493, L113). Preliminary two-dimensional numerical simulations of the RT model have been performed which produce results consistent these observations, assuming compressible fluids and a thin initial cloud. Since the radiation may impact the surface at an angle, a ‘Tilted Radiation’ instability can cause the spikes to translate as waves whose tips may ‘break’, producing the small gas ‘bullets’ visible near the Pillars in images taken by the Hubble Space Telescope. In an alternate model for the Pillars, the cometary model, the Pillars consist of gas swept behind dense preexisting nuclei. However, it appears difficult to reproduce the observed velocities and densities in numerical models with dense preexisting nuclei as the initial condition. The maturing field of laser astrophysics presents an opportunity for testing models for the Pillars in the laboratory. Theoretical and numerical evaluations of various models, implications for observations, and plans for verification experiments are presented. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
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