
Astronomers have realized for a few years now that Type II supernovae the kind that result from the collapse of a massive supergiant star's core explode from the inside like a ball suddenly growing a spindle, at least in some cases. Very likely, the tiny collapsing core emits two incredibly powerful jets along its axis of rotation, and these play the major role in blowing the entire rest of the star apart. In extreme cases, the jets power a gamma-ray burst directed along their flight lines after they break out of the star's poles. In lesser cases, the jets may not make it out of the star at all, but still cause the explosion to be asymmetrical. (See "Supernovae Are Not Round" in Sky & Telescope, January 2002, page 40.)
That's a Type II blast. Entirely different are Type Ia supernovae. These get their energy not from gravitational collapse inside a supergiant, but from a tiny white dwarf star that becomes overloaded with mass and explodes via thermonuclear fusion like a big hydrogen bomb (except that it's carbon, not hydrogen, that fuses).
Presumably, the added mass that nudges the white dwarf over its tipping point is gas that's been slowly spilling onto it from a close binary companion star at least according to the most widely accepted theory.
Now it appears that Type Ia supernovae are not round either.

That's what supercomputers are for. Last Friday, astrophysicists at the University of Chicago announced that they've used a supercomputer to run preliminary 3-D simulations of what happens when an overloaded white dwarf gets too burdened and thermonuclear fusion begins at a spot close to its center. They plan to do more of this modeling work using the Blue Gene/P supercomputer at Argonne National Laboratory.
As it turns out, the white dwarf doesn't detonate as if it were a ball of TNT, with the explosion proceeding in a shock front faster than the speed of sound in the material. Instead, the star deflagrates, at least at first, with a thermonuclear "flame" spreading through the star's interior slower than the local speed of sound. If a detonation goes bang, a deflagration goes whoosh.
And, weirdly, the first whooshed part forms a superhot, low-density bubble that quickly rises from the center (first two pictures above). The bubble bursts through one side of the star in less than a second, so intense is the white dwarf's gravity pulling the rest of the star's dense matter inward.

Read the press release, and watch the movies. Enjoy.