  In this letter we study the propagation of light in the neighbourhood of
magnetised neutron stars. Thanks to the optical properties of quantum vacuum in
the presence of a magnetic field, light emitted by background astronomical
objects is deviated giving rise to a phenomenon of the same kind as the
gravitational one. We give a quantitative estimation of this effect and we
discuss the possibility of its observation. We show that this effect could be
detected monitoring the evolution of the recently discovered double neutron
star system J0737-3039.
