  We study the structure of hybrid stars with the Field Correlator Method,
extended to the zero temperature limit, for the quark phase. For the hadronic
phase, we use the microscopic Brueckner-Hartree- Fock many-body theory. The
comparison with the neutron star mass phenomenology puts serious constraints on
the currently adopted values of the gluon condensate $G_2 \simeq 0.006-0.007
\rm {GeV^4}$, and the large distance static $Q \bar Q$ potential.
