2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/193572We review the main results obtained in the literature on quasi-normal modes of compact stars and black holes, in the light of recent exciting developments of gravitational wave detectors. Quasi-normal modes are a fundamental feature of the gravitational signal emitted by compact objects in many astrophysical processes; we will show that their eigenfrequencies encode interesting information on the nature and on the inner structure of the emitting source and we will discuss whether we are ready for a gravitational wave asteroseismology.25 pages, 7 figures, to appear on Gen. Rel. GravGeneral Relativity and Quantum CosmologyAstrophysicstext