Hunting for Alien Worlds

Hour 2:           How many earth-like or at least habitable planets might be out there for us to discover? We’ll talk this hour with planet hunter and Harvard University Professor of Astronomy Dimitar Sasselov. His new book is “The Life of Super-Earths: How the Hunt for Alien Worlds and Artificial Cells Will Revolutionize Life on Our Planet” (Basic Books, 2012).