CHICAGO (Reuters) - A Dutch primary school teacher and amateur astronomer has discovered what some are calling a "cosmic ghost," a strange, gaseous object with a hole in the middle that may represent a new class of astronomical object. The teacher, Hanny van Arkel, discovered the object while volunteering in the Galaxy Zoo project, which enlists the help of members of the public to classify galaxies online. "At first, we had no idea what it was. It could have been in our solar system, or at the edge of the universe," Yale University astrophysicist Kevin Schawinski, a member and co-founder...