This purple star map is our best guess at the shape of the universe at half its current age, according to a new simulation from a research team at Argonne National Lab. The project is called the Hardware / Hybrid Accelerated Cosmology Code (HACC), an attempt to use supercomputers to model the intricate physics of mass in an expanding universe. The project tracks roughly 1.1 trillion particles as they expand and cohere, nearly four times larger than the scale of previous simulations. The hope is that by understanding the patterns of matter in the universe, cosmologists can track down the dark matter that experts estimate composes roughly 25 percent of our universe.



Image courtesy of J. Insley and the HACC Team at Argonne National Laboratory

A picture of how the structure of the universe formed

To get there, the project needed help from some of the most powerful supercomputers on earth, drawing processor time from Titan at OCLF, Sequoia at Lawrence Livermore Lab, and Mira at Argonne Labs. Running on Titan, the simulation used over 25 petaflops of peak processing power, a speed that only one other computer in the world could manage. The simulation architecture also had to be unusually flexible to work across all three machines, and the code has been nominated for a high-performance computing award as a result. But researchers are quick to say that what's happened so far is still just a trial run, designed to test out the architecture's capabilities. "The hope is that starting in January, we'll run a mix of medium-sized simulations on Titan along with one or two really large ones," project leader Salman Habib told The Verge.

The result of all that computing power is an intricate picture of how the structure of the universe formed, tracking the trillions of particles as they interact and form more complex structures. The simulation shows the universe at roughly 7.4 billion years after the big bang (or roughly 6.4 billion years ago), imagining the development of the so-called "cosmic web," while taking into account modern ideas of dark energy. "As time evolves, the initial perturbations become clumpy mass distributions, which are dominated by dark matter," says Habib, "and from that, the ordinary matter forms into galaxies and stars."