  We consider a gravitating spherically symmetric nonrelativistic configuration
consisting of a massless chameleon scalar field nonminimally coupled to a
perfect isothermal fluid. The object of this paper is to show the influence of
the chameleon scalar field on the structure and evolution of an isothermal
sphere. For this system we find static, singular and regular solutions
depending on the form of the coupling function. A preliminary stability
analysis indicates that both stable and unstable solutions exist. For unstable
configurations, by choosing the special form of the coupling function, we
consider the problem of the gravitational collapse by applying the similarity
method.
