Scientists say the incredibly bright supernova was likely two stars

Back in September of 2006, a star in the distant Perseus constellation exploded. When the star exploded, it was 50 billion times brighter than the Sun. For 70 days, the incredibly bright explosion grew brighter and brighter until it was ten times brighter than its home galaxy.What baffled scientists about the explosion was that it was hundreds of times more powerful than a typical supernova. It was so bright that it was termed a "hypernova" and was the brightest stellar explosion ever detected. Scientists have puzzled over what made the explosion so bright for over a decade. More than a decade later, scientists think they have the answer.

Scientists have been reanalyzing the emission lines radiating from the explosion about a year after it peaked. The team found lots of iron in the emissions, which they say could only happen as the result of a supernova interaction with a preexisting layer of stellar material that was ejected hundreds of years before the supernova.

As for where the material came from, one scenario is that the explosion, dubbed SN 2006gy, began with not one star, but two. The team says that a candidate scenario predicts a binary progenitor system where a white dwarf spirals into a giant or supergiant companion star. This sort of collision is rare.

The scientists say when collisions of this sort do happen, they splash the area around with a gassy envelope of stellar material as the two cores slowly merge. If that merger occurred 10 to 200 years before the supernova was detected, the stars could have released a gassy envelope that lingered. When the star finally went supernova, the gassy envelope could amplify the brightness to levels seen in the blast.