Caltech cosmic simulation shows why black hole disks are chewy, like cakes

You might not associate “black holes” with “moist angel food cake,” but think again. Researchers at Caltech recently developed a simulation to better understand how black holes work and made the connection to cake. While not as spectacular as NASA’s simulation where spectators dive into a black hole, Caltech’s simulation challenges theories that have been around for 50 years.

The new information concerns black hole disks, also called accretion disks, which are clumps of stellar debris and gas that encase black holes. For decades, the theory was that thermal pressure caused by the shifting of gas in black hole disks kept the disks stable around the black hole. The problem is, black holes don’t look like they’re supposed to according to theory. In theory, accretion disks should be flat, but astronomical observation shows that the disks are actually fluffy.

In this simulation, Caltech researchers attempt to recreate a black hole and then perform what they call a “super zoom” to observe its behavior. The simulation involves solving the same sets of fundamental equations billions of times to see how black holes evolve.

“Our theories told us that the disks should be flat like pancakes,” says Phil Hopkins, professor of theoretical physics and leader of the Caltech research team. “But we knew that wasn’t true, because astronomical observations reveal that the disks are actually soft, more like angel food cake. Our simulation helped us understand that magnetic fields support the disk material, making it softer.”

Magnetic fields – no, not the tape

Zooming in on the simulation, the researchers can see the dance of radiation, gravity, magnetic fields, and heat as they “interact in a nonlinear way in this chaotic, disordered system,” Hopkins says. In the video, red represents the energy from the magnetic fields while blue represents the energy from the heat. The researchers expected heat to be the dominant type of energy controlling the system. Instead, the simulation showed that it was the magnetic fields that controlled the system, rather than heat.

“Because the magnetic fields are so strong, the predictions are qualitatively different from theories we’ve had for decades,” Hopkins explains in the video. “So, for example, magnetic fields can actually hold matter together and keep it from collapsing under gravity. So you’re looking at a thick ring of matter around the black hole instead of a flat disk.”

Scientists have been studying black holes since Albert Einstein predicted their existence over 100 years ago. However, because black holes are notoriously hard to find, very distant, and don’t behave like other celestial bodies, scientists have mostly turned to simulations to try to understand how they work. Sometimes, these simulations can help scientists understand what’s really going on in one of space’s greatest mysteries.