Stellar perturbations of the cometary cloud

Using a statistical approach stellar perturbation of the cloud of comets surrounding the Solar System which was suggested by Oort (Bull. Astr. Instn.; 11: 91 (1950)), have been investigated. It is shown that the cloud radius is approximately 105AU, the mean 'thermal' velocity in the clouds is approximately 110 ms-1, and the resulting perihelion distribution in the planetary region is uniform with q. Stars passing through the Oort cloud over the history of the Solar System have ejected at least 9% of the initial population and have randomized the orbits of the remaining comets so as to leave little record of their initial state. (U.K.)