Evolution of Comets

Comets that were ejected by giant planets to the Oort cloud during the formation and evolution of planetary systems may get back to the orbits in the vicinity of the Sun with a time lapse under the gravitational influence of the same planets. The evaporation of cometary nuclei due to the solar radiation impact results in releasing a solid dust component from comets. We consider a numerical model of comet transformation to dust streams that move along cometary orbits around the Sun. The lifetime of dust streams, which are formed on the orbits of their parent comets, has been estimated. In the other planetary systems, which contain giant planets satisfying the condition (where m and M are the masses of a planet and a star, respectively, r is the radius of a planet, and a is the semimajor axis of its orbit around the star), comets evolve in the same way. From the analysis of the interaction of the Oort cloud objects and the Sun with the passing-by stars and stellar clusters, it follows that a dense part of the Oort cloud is apparently limited in size; and we estimate this size.