558: Supernova SN 2006gy Astronomy Cast 558: Supernova SN 2006gy by Fraser Cain & Dr. Pamela Gay We've been following this story for more than a decade, so it's great to finally have an answer to the question, why was supernova 2006gy so insanely bright? Astronomers originally thought it was an example of a supermassive star exploding, but new evidence provides an even more fascinating answer.