Where did the Oort Cloud come from?
The origin of the Oort Cloud is another unresolved problem. It seems clear that the Oort objects could not have formed in their present locations because the material at those distances would have been too sparse to condense. The only solution that makes sense is that these icy bodies coalesced in the vicinity of Jupiter, Saturn, Uranus, and Neptune, and were subsequently hurled into the Oort Cloud by gravity-assists from the giant planets. If it were the case that the Oort Cloud comets originated at a wide range of distances, from the orbit of Jupiter to that of Neptune, and therefore at a wide range of ambient temperatures, this would explain the differences in composition observed in long-period comets. Recent work suggests that the Oort Cloud may even contain a small percentage of asteroids, made of rock rather than predominantly of ice.4 References • Brunini, A., and Fernandez, J. A. “Perturbations on an Extended Kuiper Disk Caused by Passing Stars and Giant Molecular Clouds,” Ast
