An Etymological Dictionary of Astronomy and Astrophysics
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The → minimum mass for an → interstellar cloud below which the → thermal pressure of the gas prevents its → collapse under the force of its own → gravity. It is given by the formula M_J = (π^5/2 / 6) G ^-3/2ρ₀^-1/2c_s³, where G is the → gravitational constant, ρ₀ the initial → density, and c_s the isothermal → sound speed. It can be approximated to M_J ~ 45 (T_K) ^3/2 (n_cm^-3) ^-1/2 in units of solar masses, where T_K is the temperature in → Kelvin, and n_cm^-3 the gas density per cm³. High density favors collapse, while high temperature favors larger Jeans mass. See also: → thermal Jeans mass, → turbulent Jeans mass.

→ Jeans; → mass.

The → Jeans mass when → turbulence is insignificant.

→ thermal; → Jeans; → mass.

The characteristic mass for → cloud fragmentation in a → turbulent medium. While the standard → Jeans mass depends simply on the gas mean → density and → temperature, and fragmentation is purely gravitational, turbulent Jeans mass depends strongly also on the → Mach number (Chabrier et al. 2014, arXiv:1409.8466).

→ turbulent; → Jeans; → mass.