An Etymological Dictionary of Astronomy and Astrophysics

The upper value of mass that a → Bonnor-Ebert sphere must have in order that → hydrodynamic equilibrium be maintained. This → critical mass is given by: M_crit = 1.18 (a⁴/G^3/2)P_ext^-1/2, where a = (kT/m)^1/2 is the isothermal → sound speed inside the sphere, G is the → gravitational constant, and P_ext the pressure of the external medium (see, e.g., F. H. Shu, 1977, ApJ 214, 488).

See also: → critical; → Bonnor-Ebert mass.