(Image: NASA)
There's more than one way to make a star explode. Astronomers have two competing explanations for how a certain kind of blast called a type Ia supernova happens - now it seems both can be right.
Type Ia supernovae are particularly useful explosions. They're known to all have the same brightness, so they can be used as "standard candles" to measure cosmic distances. That feature made them key players in the discovery of dark energy, the mysterious substance that is thought to be pushing the universe apart at an ever-accelerating rate. The discoverygarnered three scientists the Nobel prize in physics last year.
We don't know much about how these supernovae form, though, which limits how well they can help us measure cosmic distances, and in turn how much we can learn about dark energy.
We do know that a type Ia supernova starts off as a white dwarf, the dense core of a dead star, but there are two popular theories for what happens next. One says that supernovae form when two white dwarfs in a binary system spiral towards each other and the heavier stellar corpse rips the lighter one apart until enough material from the lighter star gets incorporated into the heavier one to light the supernova fuse. The other option is a white dwarf that steals material slowly from an ordinary, sun-like companion star, until the white dwarf ignites.
