  We apply the realistic shell model which includes the coupling between
many-particle (quasi-)bound states and the continuum of one-particle scattering
states to the spectroscopy of mirror nuclei: $^8$B and $^8$Li, as well as to
the description of low energy cross sections (the astrophysical S factors) in
the capture reactions:$^7Be(p,\gamma)^8B$ and $^7Li(n,\gamma)^8Li$.
