Dynamical evolution of the nucleus of comet Hartley 2 and Asteroid Itokawa

Cometary nuclei are being actively studied using spacecrafts. In November 2010, the Deep Impact spacecraft (EPOXI project, NASA) approached the nucleus of comet 103P/Hartley 2 and returned images of this small celestial body having a dumbbell shape with a smooth neck. Since rotation of the nucleus leads to centrifugal forces, it is assumed that the dumbbell neck appeared as the result of their effect and the neck is lengthening slowly but continuously, which should eventually result in fragmentation of the nucleus. This paper considers dynamical evolution of the nucleus of comet Hartley 2. Calculations show that centrifugal forces exceed gravitational forces in the narrow part, and the nucleus can indeed undergo upcoming breakup and fragmentation into two parts. If there are no external perturbations, both parts of the celestial body will drift apart to a distance of less than 1 km from each other. The nucleus of comet Hartley 2 is an observed example of breakup of a celestial body. Asteroid Itokawa is considered, which has a similar feature but does not seem to undergo breakup.