An Etymological Dictionary of Astronomy and Astrophysics
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Mechanics: The condition of a moving mechanical system when the accelerating force is balanced by an imaginary kinetic reaction according to → d'Alembert's principle. See also → static equilibrium; → thermodynamic equilibrium.

Dynamic, adj. from → dynamics; → equilibrium.

The state of a star when all its internal forces are in equilibrium. The main forces are gas pressure, radiation pressure due to thermonuclear fusion that tends to disrupt the star, and the opposing gravity. → hydrostatic equilibrium.

→ hydrodynamic; → equilibrium.

The assumption that all distribution functions characterizing the material and its interaction with the radiation field at a point in the star are given by → thermodynamic equilibrium relations at local values of the temperature and density.

→ local; → thermodynamic; → equilibrium.

A physical condition in which the assumption of the → local thermodynamic equilibrium does not hold.

→ non-; → local thermodynamic equilibrium.

The condition of a → thermodynamic system in which the available → energy is distributed uniformly among all the possible forms of energy. Furthermore, all → thermodynamic process es must be exactly balanced by their reverse processes. For example, inside a star there will be as many → ionizations of helium per second as there are → recombinations of free electrons and helium ions. Se also → local thermodynamic equilibrium (LTE).

→ thermodynamic; → equilibrium.