The remainder of the last century has seen compact objects been the centre study of general relativist astrophysics especially black hole-black hole, black hole-neutron star and neutron star-neutron binaries which are said to be the main sources of gravitational radiation in our universe. Convincing major research results have been obtained thus far prompting the development of gravitational wave astronomy. In the distant future, gravitational wave detectors which are being build will detect gravitational wave signals from compact relativistic binaries sources and also from relativistic collapsing sources. In order to theoretically study these sources in this book, we specifically linearize gravity within a Schwarzschild geometry using the Bondi-Sach formalism and we study the resulting perturbations , and for the first time, we obtain quasi-normal modes of a Schwarzschild white hole. We then apply these perturbations to study the emitted gravitational radiation at null infinity from a relativistic system consisting of a point particle in close orbit around a stationary Schwarzschild black hole.