|Image and caption: Nature|
The M82 galaxy is a frequent imaging target because of its unusual cigar shape, and so it might be possible to identify what lay in the region before the supernova event by going back to historical surveys of the galaxy.
Based on the early spectral readings, this supernova is thought to be of Type Ia, a class which reaches predictable absolute brightness peaks-- their brightness as seen from earth is then a function of their distance, and thus they can be used as standard candles to determine the distance of far-away objects. Because of their importance to astronomical surveying, there is a lot of interest in what exactly leads to their big explosion. Although the parent body for this type explosion is almost certainly a white dwarf star, the details of the detonation have been hard to simulate with computer models. The 1987 supernova was of a different type, and its parent body was probably a blue supergiant. The different classes synthesize heavier elements to different degrees. For example with Aluminium-27 is produced at a bit more than 200 fold greater abundance by Type II supernovae compared to type Ia.