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By considering the Jeans mass fragmentation of a gas cloud we derive a minimum fragment mass of |0025 (mH/m) ^16/7 (k0/k1) ^1/7\, M_, \, wher\, k0/k1| is the ratio of the electron scattering opacity to the gas opacity at the final fragmentation, and |m/mH| is the ratio of the mass of a gas particle to that of the hydrogen atom. For a dark molecular cloud this would give a |0007\, M_| fragment. This result is very insensitive to changes in the opacity of the gas. We have also studied the effects of isotropic blackbody radiation on the minimum mass, with particular reference to primeval star formation, and find it important for epochs with redshift z |\, 27| A number of different opacities were considered and we conclude that the most important source of opacity, both for present and past star formation, is dust grains.
Low et al. (Sun,) studied this question.