Background: The neutron skin of a heavy nucleus as well as many neutron-star properties are highly sensitive to the poorly constrained density dependence of the symmetry energy. Purpose: To provide for the first time meaningful theoretical errors and to assess the degree of correlation between the neutron-skin thickness of ${}^{208}$Pb and several neutron-star properties. Methods: A proper covariance analysis based on the predictions of an accurately-calibrated relativistic functional {\sl "FSUGold"} is used to quantify theoretical errors and correlation coefficients. Results: We find correlation coefficients of nearly one (or minus one) between the neutron-skin thickness of ${}^{208}$Pb and a host of observables of relevance to the structure, dynamics, and composition of neutron stars. Conclusions: We suggest that a follow-up PREX measurement, ideally with a 0.5% accuracy, could significantly constrain the equation of state of neutron-star matter.

15 pages, 9 figures, 5 tables