An Etymological Dictionary of Astronomy and Astrophysics

The equation describing the → hydrostatic equilibrium in a star, expressed as: dP/dr = -GMρ/r², where
P and M are the mass and pressure of a spherical shell with thickness dr at some distance r around the center of the star, ρ is the density of the gas, and G the → gravitational constant.

See also: → hydrostatic; → equation.