The Case of the Missing Supernova . ... About 700 years ago, light from a tremendous explosion reached Earth that should have appeared almost as bright as a full Moon. ... The mystery was uncovered by Wan Chen and Neil Gehrels ( NASA/GSFC ) when studying the source of radioactive elements toward the Vela supernova remnant . ... The above picture of GRO/RX J0852 was taken in gamma-ray light with the Compton Gamma-Ray Observatory and is shown in false-color. ... NASA Official: Jay Norris. ...