Now, knowing all the basic processes and mechanisms of cooling and heating, we can write the equation of thermal balance in the form of nG (T) = n2 (T). Write the equation of ionization balance needed to know population levels. Solving, we get the equilibrium temperature T (n). Given that the substance in the interstellar medium is discharged, that is, is an ideal gas, under Mendelleva-Clapeyron equation to find the equilibrium pressure P (n). And found that the relationship more like a gas equation of state Van der Valsa: there is pressure area, where a value of p corresponds to the three equilibrium enacheniya n. A decision on the negative derivative is unstable on small perturbations: at a pressure higher than the environment it will grow until a balance with less density, but with a smaller picture with precision, but on the contrary. This explains the observed dynamic equilibrium rarefied interstellar medium, and a dense cloud of interstellar gas.
In the real environment situation is much more complicated. Firstly, there is a magnetic field, prevents compression of the office, unless it occurs along the field lines. Second Interstellar Medium is in continuous motion and its local properties are changing continuously, there are new sources of energy and the old disappear. So that the condition of thermal equilibrium can not be implemented. In the third place, except there is a thermodynamic instability of gravity and magnitogidrodinmicheskaya. And this is without taking into account all kinds of disasters in the form of outbreaks of supernovae, tidal influences passing nearby galaxies, or passage of gas through the spiral arms of Galaxy.