2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6233We report on a possible correlation between the mass ratio and period ratio of pairs of adjacent planets in extra-solar planetary systems. Monte-Carlo simulations show that the effect is significant to level of 0.7%, as long as we exclude two pairs of planets whose periods are at the 1:2 resonance. Only the next few multiple systems can tell if the correlation is real.8 pages, 2 figures, published in The Astrophysical Journal LettersAstrophysicstext