Supernova, Two Ways

Source: Sky & Telescope

This simulated image depicts the explosive death of a white dwarf as a Type Ia supernova with a stellar companion. When the supernova explodes (dark brown), its ejected material slams into the companion star (light blue). The violent collision produces an ultraviolet pulse, which is emitted from the conical hole carved out by the companion star.

Two new studies confirm that the white dwarfs that explode as Type Ia supernovae can approach death in two different ways.

For many years, astronomers have debated just how the white dwarf maxes out its mass. There are two scenarios: either it siphons gas from a “living” companion star until it just can’t swallow any more (called the single-degenerate model), or it merges with another dead star like itself (the double-degenerate model). The growing sense is that white dwarfs probably die both ways.

Two papers in the May 21st Nature support this suspicion. One reports an ultraviolet pulse from a supernova that, the authors say, is a telltale signal that the white dwarf was stealing material from a companion star. The other study finds no evidence for such a signal from three supernovae.