It was early one morning in February 1987 and a colleague was recounting an unthinkable rumor: A star had exploded in a galaxy next door.  the cosmic explosion—dubbed SN1987A or just 87A for short—remains the closest supernova that has been seen in nearly four centuries. Its proximity, plus the use of modern technology, allowed astronomers across the globe to catch an incredible show—one that continues today. Supernovae change the fate of entire galaxies, altering the chemical make-up of the interstellar medium and prompting the formation of new stars. They have even had quite an effect on you; the calcium in your bones, the oxygen you breathe and the iron in your hemoglobin were all elements originally unleashed in these massive stellar explosions.