  With the discoveries of very close star-planet systems with planet orbiting
sometimes at several star radius but also with well-known situations in our
solar system where natural satellites are very close to their parent planet the
validity of the ponctual mass approximation for the tidal perturber
(respectively the parent star or planet when we study the close planet or
natural satellite dynamics) has to be examined. In this short paper, we
consider this problematic using results coming from a complete formalism that
allows to treat the tidal interaction between extended bodies. We focus on its
application to a simplified configuration.
