2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/230426A simple and {\it innocent} modification of Poisson's equation leads to a modified Newtonnian theory of gravitation where a localized and {\it positive} energy density of the gravitational field contributes to its own source. The result is that the total {\it active gravitational mass} of a compact object is the sum of its {\it proper mass} and an {\it evanescent gravitational mass} which is a mass equivalent to the gravitational energy.6 pages,minor changesClassical PhysicsGeneral Relativity and Quantum Cosmologytext