Gravitational Wave Scintillation by a Stellar Cluster

General Relativity predicts the existence of gravitational waves that propagate in the vacuum with the speed of light. Analogously to electromagnetism, it is expected that gravitational waves might also be scattered by intervening particles 1,2,3 and micro-lensed by compact objects along the line of sight 4,5,6. Moreover, gravitational waves will be diffracted as they pass through a distribution of objects, each of which acts as an obstacle (or slit). Of course, these effects are expected to become apparent only if the linear sizes of the intervening particles are comparable to the gravitational radiation wavelength in the range 10 − 10 cm. We consider a stellar cluster as the diffracting object and concentrate in particular on that possibly hosted in the center of the Milky Way and surrounding the central black hole Sgr A. There are two types of diffraction phenomena discussed: the Fraunhoffer 7 and Fresnel approximation. In our case only the second is relevant since the first approximation involves infinite source-cluster and cluster-observer distances. We determine the conditions under which the diffraction effects may be measurable. It turns out that a gravitational wave scintillation effect, analogous to the well