When labeling astronomers, we generally fall into a very small number of categories. There are the observational folks, the computational folks, the theorists, and the instrument builders. That’s most of us, and many of us will wear more than one of those labels during our lifetimes. Our combined efforts build the instruments that are used to observe our skies and test our theories against reality, and when those datasets get big enough and the theories get complex enough, we throw computational might into the problem.

But sometimes our computers just can’t handle the complexities of the universe in the needed detail. The interactions of myriad particles in planetary atmospheres and the propagation of shock waves in supernovae are all problems that we can approximate in computers, but our approximations just don’t look like the reality we observe. Situations like these are when we turn to one of the rarest kinds of astronomer – the laboratory astrophysicist. These folks build equipment that simulates the specific conditions of different astronomical events and recreates our universe in a box, or in the case of today’s top story, in a pizza-shaped wedge.

The Hubble Space Telescope and other high-resolution systems have allowed us to see supernovae remnants as complex lumpy, bumpy systems that are each unique. Trying to recreate the complex leading edge of these systems has proven more than a computer model can handle. Now though, there is a laboratory option. Researchers at Georgia Tech have created a supernova simulator in their lab. Like computational simulators, it only looks at a section of the explosion – a wedge expanding away from a simulated core – but this system provides enough three-dimensional particle interactions to recreate supernova physics in a way that has previously just not been possible.

In an actual supernova, the core of a star will collapse after it runs out of fuel to power the light-producing nuclear reactions that normally support the star. This collapse triggers a powerful explosion that pushes the high-density star material in the inner regions of the star outwards, where it mixes violently with the surrounding lower density materials. These layers have fairly defined boundaries, and in this supernova simulator, this system is recreated as an actual explosion that pushes up through the two different layers of high-density and low-density gas.  According to the press release: Heavier gas in inner layers stabs turbulent outcrops into lighter gas in the outer layers. Then behind the blast wave, pressure drops, stretching the gases back out for a different kind of turbulent mixing. The final structures of the supernova are shaped in part by the naturally forming irregularities at the boundaries between the two densities of gas. These perturbations are stretched and skewed at angles when blasted by the explosions shock wave.

The Supernova-in-a-Wedge machine allowed researchers to take high-speed images of what was going on at the density boundary and capture the formation of these iconic supernovae structures. Along with the regular bumps and bubbles, they also observed turbulent spikes of high-density gas pushing into the low-density region, and bubbles of light gas trapped inside areas of high-density gas.

In addition to defining how these shockwave-driven structures form, this physical simulator allows researchers to better understand the timescales of these structures’ evolution. This will ultimately help us better date the formation of observed supernova remnants.

This is cool research that makes it clear that sometimes you need to try and recreate what you see, and it is only in that recreation that you can understand what you see.

More Information

Georgia Tech Research Horizons article 

 “Supernova Hydrodynamics: A Lab-scale Study of the Blast-driven Instability using High-speed Diagnostics,” Benjamin Musci et al., 2020 June 17, The Astrophysical Journal