2008/04/25 by S. Kimeswenger, Kimeswenger, S., A. A. Zijlstra +13
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.0804.4069
to appear in the proceedings of HYDEF07, Tuebingen 2007
arxiv created 2008/04/25 · arxiv updated 2009/12/01
While in the past spherodicity was assumed, and still is used in modeling of most nebulae, we know now that only a small number of planetary nebulae (PNe) are really spherical or at least nearly round. Round planetary nebulae are the minority of objects. In the case of those objects that underwent a very late helium flash (called VLTP objects or ``born-again'' PNe) it seems to be different. The first, hydrogen-rich PN, is more or less round. The ejecta from the VLTP event, in contrast, are extremely asymmetrical.