Interstellar comets? – Free Online Library Essay

Most experts in the field accept the “classic” idea that the Oort cloud, the source of comets, is populated by objects left over from the formation of the solar system. However, Michael A’Hearn of the University of Maryland in College Park wonders whether some comets might be of interstellar origin. Specifically his question is whether, as the solar system moves through the giant molecular clouds (GMCs) that populate interstellar space, the Oort cloud can be alternately stripped of its contents by the gravity of such clouds and then replenished from the matter in the GMCs.

Studying the physical chemistry of comets, A’Hearn finds that they can be put into two groups according to their composition. He suggests that this may mean that one group represents matter put into the Oort cloud by the last GMC the solar system passed through, while the other represents the last previous GMC.