... Comet Hale-Bopp Inbound . ... Headed toward the inner Solar System, the much anticipated Comet Hale-Bopp has promised to put on a big show next spring. ... Interstellar space is filled with extremely tenuous clouds of gas which are mostly Hydrogen. ... Light flooded the local interstellar neighborhood, illuminated this existing gas cloud, excited the existing hydrogen, and hence caused the red emission. ... Here a very distant QSO happened to be placed right behind a massive galaxy. ...