  In the paper we discuss equilibrium states of stars, using a simplified
analytic model. A star is considered as self-graviting body of gas. We use a
condition for the equilibrium state of the body in the form of a differential
equation, which relates the pressure distribution and mass density in the body.
The density distributions of constant, potential, gaussian, and exponential
forms are discussed. Exact expressions for the distribution of mass and
pressure along the radial direction, and the central pressure were obtained.
