Binary star death explains interacting supernova mystery

Binary stars dying together may explain a mystery surrounding interacting supernovas. New research suggests that when one star in a binary pair expands into a red giant, it sheds material onto its companion, forming a cocoon. This cocoon then interacts with the supernova shockwave. This mass transfer must occur shortly before the star's death for the cocoon to remain dense enough to create the observed bright explosions.