Astronomers believe that many planets – including our own solar system – emerged from giant disks of gas and dust spinning around stars. To understand these cosmic mechanisms, researchers have typically used simulations to separately examine planetary development and magnetic field formation. Now, new work by researchers from the University of Zurich and the University of Cambridge has unified these fields of study in a single simulation for the first time ever.
Researchers knew that planets likely formed as a result of gravitational instabilities in the disks that allowed particles to congeal together, slowly forming planets over hundreds of thousands of years. With the new study, the research team aimed to examine the effects that magnetic fields have on planet formation in the context of those gravitational instabilities.
To do that, they modified a hybrid mesh-particle method that calculated the mass and gravity using particles, creating a “virtual adaptive mesh” that allowed the researchers to simultaneously incorporate magnetic fields, fluid dynamics and gravity.
Applying that method required supercomputing power. The researchers turned to Piz Daint, the in-house Cray supercomputer of the Swiss National Supercomputing Centre (CSCS). Piz Daint’s 5,704 XC50 nodes each pack an Intel Xeon E5-2690 v3 CPU and an Nvidia Tesla P100 GPU, and its 1,813 XC40 nodes each carry two Intel Xeon E5-2695 v4 CPUs. The two sections stack up at 21.2 Linpack petaflops and 1.9 Linpack petaflops respectively, placing 6th and 185th on the most recent Top500 list of the world’s most powerful supercomputers.
After running the simulations on Piz Daint, the researchers got some very interesting results. For some time, the astronomy community has puzzled over why planets spin slower than the disks from which they were born. But now, it seems, they might have their answer.
“Our new mechanism seems to be able to solve and explain this very general problem,” said Lucio Mayer, professor of computational astrophysics at the University of Zurich and project manager at the National Centre of Competence in Research PlanetS.
“The simulation shows that the energy generated by the interaction of the forming magnetic field with gravity acts outwards and drives a wind that throws matter out of the disk,” Mayer said. “If this is true, this would be a desirable prediction, because many of the protoplanetary disks studied with telescopes that are a million years old have about 90 percent less mass than predicted by the simulations of disks formation so far.”
The researchers believe that that matter-ejecting mechanism is the culprit behind the loss of angular momentum in the disks and, ultimately, the planets they birth. The discovery of this mechanism, of course, was only made possible by conducting their unified simulation on Piz Daint.
To read CSCS’ Simone Ulmer’s article discussing this research, click here.
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