When an aging star about 10 times as massive as our sun runs low on light, easy-to-fuse elements, its nonfusing iron core collapses. The star's interior then rebounds like a spherical piston, exploding into a type II supernova. Using a supercomputer at the Leadership Computing Facility at Oak Ridge National Laboratory in Tennessee, astrophysicists have shown that neutrinos play a key role in powering the shock wave that tears through the star. This rendering shows the hydrodynamic flow of matter in a giant star's core. Tan areas show higher entropy, or heat; blues and greens are comparatively cooler surges of matter.