Angular momentum of two collided rarefied preplanetesimals and formation of binaries

Mean angular momentum of two objects encountering from almost circular heliocentric orbits up to their Hill spheres is studied. Results of these studies are used for discussion of models of formation of binaries at the stage of rarefied preplanetesimals. Some collided rarefied preplanetesimals could have a greater density at distances closer to their centres, and sometimes there could be two centres of contraction inside the rotating preplanetesimal formed as a result of a collision of two rarefied preplanetesimals. In particular, binaries with close masses separated by a large distance and with any value of eccentricity of the mutual orbit of the secondary and the primary components could be formed. The observed separation distance can show the order of characteristic sizes of encountered preplanetesimals. Formation of some binaries could be caused by that the angular momentum that was obtained by a rarefied preplanetesimal was greater than that could exist for a solid body. During contraction of such rotated rarefied preplanetesimal, some material could form a disc of material moved around the primary. One or several satellites of the primary could be formed from this cloud. The angular momentum of any discovered trans-Neptunian binary is smaller than the typical angular momentum of two identical rarefied preplanetesimals having the same total mass as the discovered binary and encountering up to the Hill sphere from circular heliocentric orbits.