  A new relation between the neutron skin of a heavy nucleus and the radius of
a neutron star is proposed: the larger the neutron skin of the nucleus the
larger the radius of the star. Relativistic models that reproduce a variety of
ground-state observables can not determine uniquely the neutron skin of a heavy
nucleus. Thus, a large range of neutron skins is generated by supplementing the
models with nonlinear couplings between isoscalar and isovector mesons. We
illustrate how the correlation between the neutron skin and the radius of the
star can be used to place important constraints on the equation of state and
how it may help elucidate the existence of a phase transition in the interior
of the neutron star.
