By Nadia Drake
There are two ways to light a cosmic candle. One technique calls for two white dwarf stars; another positions a white dwarf near a larger stellar companion. Both combinations produce type 1a supernovas (pictured here), massive stellar explosions that act as “standard candles” for gauging astronomical distances.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2012/05/15867.jpg?resize=300%2C232&ssl=1)
Type 1a supernovas are triggered when white dwarfs gain weight, igniting a runaway thermonuclear reaction that destroys the dwarf, producing a fireball of predictable brightness. For a long time, astronomers disagreed over what sorts of ingredients were needed to make the white dwarf go boom.