Tidal splitting and rotational breakup of solid biaxial ellipsoids

New expressions for the Roche limit for solid biaxial ellipsoids are derived, taking the size, shape, density, material strength, and rotational period of the object into account. It is shown that the shape has a significant effect on the tidal splitting distance, so that spherical bodies are more stable than oblate spheroids, which in turn are more stable than prorate spheroids. New expressions for the critical rotational breakup period (for objects in free space) are derived, and are used to put constraints on the density and material strength of a collection of comets, for which size, shape, and period have been estimated. This investigation shows that the notion of very low cometary material strengths (less than or similar to 100 Pa) is consistent with observational data. (C) 2001 Academic Press.