Two physical explanations of the nonextensive parameter in a   self-gravitating system
  We present two possible physical explanations of the nonextensive parameter in a self-gravitating system. One is related to the detailed balance in such system. With the detailed balance, the statistical balance of molecular energy is reached, under which the radiation energy "stored" in the molecules becomes important. Then the relation between the nonextensive parameter and the storage coefficient which measures the ability of molecules to store the radiation energy is constructed. The other explanation is from one dimensionless quantity called (logarithmic) temperature gradient defined in the stellar physics. In view of this, we find that in order to keep the nuclear reactions alive inside the Sun, the ratio of radiation pressure to the total pressure in the core must be more than 0.2833. 
Yahui Zheng and Jiulin Du
cond-mat.stat-mech astro-ph.SR