When nothing else works, use dynamite and make something explode, right? At least that’s what some astronomers may feel now, after many years of discussions about wether supernovas of type Ia originate from one regular star that is sucked in by gravity from a white dwarf, or from two colliding white dwarfs.
Well, after a very rare outburst of radiation from a type Ia supernova, some 300 million light-years away from Earth in the galaxy IC 831, scientists found evidence that the radiation likely came from a collision between a normal star and a white dwarf. The double-generation theory thereby gained as much credibility as the more commonly recognized single-generation theory.
It was only thanks to the swift action to point the space based NASA telescope Swift and others in the direction of the just reported supernova explosion, that this outburst of radiation could be registered. With only a couple of days delay, the radiation wouldn’t have been detected. Both European, Israeli and American astronomers were quick to turn their telescopes, both ground based and space based, towards the explosion, now named iPTF14atg (after all, it was an explosion, so how could it be named differently?).
The ultraviolet light indicated strongly that the supernova had occurred as a fully evolved star which had been absorbed by a white dwarf, rather than as a result of two colliding white dwarfs.
Usually it’s extremely hard to detect white dwarfs in a supernova explosion, because the white dwarfs emit very little light, being dying stars with no hydrogen left to fuel their fusion. Supernovas are often so bright that their home galaxy gets outshined.
By looking at images of the star before it exploded, it’s possible though to identify the parent star, if that’s what caused the supernova. However, for these pre-supernova identifications to be possible, the supernova would have to be occurring in our own galaxy or at similar distances, since these type Ia explosions are so rare.
The conclusions from the new supernova data were published in the journal Nature, May 21, and will be useful as scientists develop their tools to accurately measure the expansion of the Universe.