For decades, astronomers have struggled to explain why planets with intermediate masses – such as Uranus and Neptune – overwhelmingly outnumber planets of other sizes. Now, using the power of supercomputing, researchers from the Universities of Cambridge and Zurich may have solved this long-standing mystery.
“When planets form from the so-called protoplanetary disk of gas and dust, gravitational instabilities could be the driving mechanism,” explained Lucio Mayer, a professor of computational astrophysics at the University of Zurich and co-author of the study, in an interview with the University of Zurich’s Arian Bastani. “But over shorter distances – the scale of single planets – another force dominates: That of magnetic fields developing alongside the planets.”
As Hongping Deng, the study’s lead author and a research fellow at the University of Cambridge, explains, understanding how planets are born means understanding the balance between these two forces. “To get a complete picture of the planetary formation process, it is … important to not only simulate the large scale spiral structure in the disk – the small scale magnetic fields around the growing planetary building blocks also have to be included,” he said.
Gravity and magnetism are difficult to integrate into a single model, so when the researchers developed code to accurately represent the processes, they supercharged it with supercomputing: specifically, the Piz Daint system at the Swiss National Supercomputing Center (CSCS). Piz Daint is a Cray system comprising 5,704 XC50 nodes and 1,813 XC40 nodes. Currently, it delivers 21.2 Linpack petaflops, placing it 12th on the most recent Top500 list of the world’s most powerful publicly ranked supercomputers.
Using the new model on Piz Daint, the researchers made a breakthrough.
“With our model, we were able to show for the first time that the magnetic fields make it difficult for the growing planets to continue accumulating mass beyond a certain point,” Deng explained. “As a result, giant planets become rarer and intermediate-mass planets much more frequent – similar to what we observe in reality.”
Another of the co-authors, Ravit Helled (a professor of theoretical astrophysics at the University of Zurich) explained that while the results are “only a first step,” they are an important first step in including more physical processes in planetary simulations.
About the research
The researcher discussed in this article was published as “Formation of intermediate-mass planets via magnetically controlled disk fragmentation” in Nature Astronomy. The paper, written by Hongping Deng, Lucio Mayer and Ravit Helled, is accessible here.
Header image: a still of the planetary formation process from the simulation.
To learn more about this research, read Arian Bastani’s article here.