Let us begin our analysis with the outermost region. In the absence of X-rays from nearby young stars, the gaseous component here is heated mainly by cosmic rays, at a volumetric rate given by equation (7.12), and by the grain photoelectric effect (equation (7.18)). The additional heating mechanism of carbon ionization (equation (7.16)) is unavailable, since that element is already fully ionized throughout the envelope. The gas cools through emission of infrared photons from
The Formation of Stars. Steven W. Stabler and Francesco Palla Copyright © 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-40559-3
Jl embedded i. interior
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