  A generic toy model of a cooling neutron star (NS) is used to analyze cooling
of NSs with nucleon and exotic composition of the cores. The model contains the
parameters which specify the levels of slow and enhanced neutrino emission as
well as the lower and upper densities of the layer where the slow emission
transforms into the enhanced one. The prospects to constrain these parameters
from the present and future observations of isolated middle-aged NSs are
discussed.
