Brightest supernovae are in a class of their own

Nature : When stars several times more massive than our Sun die, they explode into supernovae, radiating enough energy to outshine a galaxy. The radiation is sometimes produced by radioactive decay, and sometimes by the explosive release of heat, or from a collision between debris ejected by the star and material surrounding it. Six such explosions can’t be explained by any known process, writes Jon Cartwright for Nature. Robert Quimby of Caltech and colleagues think that these explosions should be classified as a new type of supernova . All six explosions are about 10 times more luminous than type Ia supernovae (the most commonly recorded type), and unlike most supernovae, their main emission is UV radiation rather than visible light. Quimby’s team has theorized that the exploding stars may have been so large that they became unstable and threw off bits of material before finally going nova. That material would then interact with the final explosion, causing the intense brightness. On the other hand, the supernovae might, in their early stages, have become magnetars—spinning, highly magnetized neutron stars. The very strong magnetic field of such stars would slow down their spin, and the excess energy of their motion may have been released to make them unusually bright.