An Etymological Dictionary of Astronomy and Astrophysics
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In astrophysics, a gaseous sphere in hydrodynamic equilibrium in which the pressure and density are related by the equation P = Kρ^(n+1)/n at each point along the radius, where K is a constant and n is the → polytropic index. The constant K depends upon the nature of the polytrope. Before the advent of computing technology, the theory of polytropes played an important role in physically modeling the structure of stars. → Lane-Emden equation.

Polytrope, from → poly- + trope, from → -tropic.

Bolgašt, from bol-, → poly-, + gašt "change, alteration," → -tropic.