Stellar Suicide 
There may be more than one way to make a white-dwarf star go “boom!” One way is through stellar thievery, while the other may be mutual suicide.
A white dwarf is the hot, dense core of a star that’s used up its nuclear fuel and cast its outer layers into space. It’s roughly as massive as the Sun, but only as big as Earth.
There’s a “weight limit” for white dwarfs -- about 1.4 times the mass of the Sun. If a white dwarf goes beyond that limit, it blasts itself to smithereens -- an explosion known as a Type 1a supernova.
One way for a white dwarf to tip beyond the point of no return is to “steal” gas from a companion star. The gas spirals toward the white dwarf and crashes into its surface. When enough gas piles up, it triggers a runaway thermonuclear explosion, like a stellar H-bomb.
But there may be a second way to create a Type 1a supernova: the collision of two white dwarfs. And in fact, a recent study suggests that’s just what happened with a supernova in a companion galaxy to the Milky Way.
Astronomers from LSU studied the expanding cloud of gas and dust from a recent supernova. They looked for evidence of a star that could have been a companion -- the star from which the white dwarf stole mass. They found none. That suggests that the explosion left nothing behind. One explanation is that two white dwarfs slammed together. Their combined mass pushed them over the limit -- triggering a double stellar suicide.
More about white dwarfs tomorrow.
Script by Damond Benningfield, Copyright 2012