Abstract: This paper points out that a planet（ or a satellite） revolving around a primary star may generate a velocity component towards the star because of kinetic energy loss due to gravitational wave emission and,if the Roche limit of the planet with respect to the primary star lies outside of the star surface,the planet,driven by the velocity component towards the star,will ultimately approach the Roche limit,where it is ripped apart by the tidal force and where the gravitational radiation terminates. The author gives an equation for computing the time at which the planet is ripped apart. A computation example is given using Saturn in the solar system as the study subject,in which the time of its ripping apart by tidal force is computed as it approaches the Sun under the influence of gravitational radiation. This philosophy is further generalized to binary stars that revolving around each other and to comets.

Key words: gravitational radiation, Roche limit, approach, tidal force, ripping apart