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.
But the new model — a three-dimensional time-dependent numerical simulation of the flow of matter inside stars — shows something a bit different: a near-chaotic interior that ejects star remnants prior to the final explosion.
"We still have the concentric circles, with the heaviest elements in the middle and the lightest elements on top, but it is if someone put a paddle in there and mixed it around. As we approach the explosion, we get flows that mix the materials together, causing the star to flop around and spit out material until we get an explosion," noted Arnett in a statement.
This explains the strange composition of supernova remnants — the ring of heavy and light elements that form nebulas around stars that went supernova. "That's what see in supernova remnants. We see those ejections of star material, and how they mix with material expelled from the star during its final explosion. Other models cannot explain this."
Relatedly, using NUSTAR data of an actual supernova, NASA put together this simulation:
And this is what a red giant looks like just prior to going supernova:
Read the entire study at AIP Advances: "Chaos and Turbulent Nucleosynthesis Prior to a Supernova Explosion."