You're looking at the first ever 3-D model of a supernova entering into the initial phase of its cataclysmic death throes. This is part of a new computer simulation that's radically changing our notions of what happens inside stars just before they explode.
The 3D model was put together by W. David Arnett, Regents Professor of Astrophysics at the University of Arizona, along with Casey Meakin and Nathan Smith at Arizona and Maxime Viallet of the Max-Planck Institut fur Astrophysik. It shows the turbulent mixing of elements inside of these massive stars which cause them to expand, contract, and spew out matter just prior to their detonation.
Looking at the top image, the white lines represent the simulated outer boundary of a stratified burning oxygen shell. The yellow portions are ashes of sulphur which are being dredged from the underlying orange core.
Previously, 2D models showed stars as a series of concentric circles, with heavier elements like iron and silicon in the center and lighter elements like carbon helium and oxygen up at the surface. These models suggested that stars would get all scrunched-up, increasing pressures and driving temperatures high enough to create neutrinos. But as neutrinos go, so too does the star's energy, causing the star to cool down and contract even further.