In 2015, after a century of uncertainty, the Laser Interferometer Gravitational-Wave Observatory (LIGO) first observed gravitational waves from the collision of black holes. A decade prior, a scientist named Carlos Lousto had used the Lonestar supercomputer at the Texas Advanced Computing Center (TACC) to generate a simulation of such an event that was so accurate that, he told TACC’s Aaron Dubrow, when the waves were detected, “it took us two weeks to realize this was really from nature and not from inputting our simulation as a test.” Now, five years later, Lousto is diving even deeper into black holes – with updated hardware at his side.

For his new round of simulations, Lousto – a professor of mathematics at Rochester Institute of Technology (RIT) is simulating black hole mergers with wildly disproportionate size ratios (128:1). Waves from such collisions are not detectable by LIGO, which can only detect waves from collisions between moderately sized black holes of more or less equal sizes. Even simulating these collisions is an extraordinarily challenging computational task, with the previous highest ratio simulated with high precision sitting at 16:1.

“Modeling pairs of black holes with very different masses is very computational demanding because of the need to maintain accuracy in a wide range of grid resolutions,” said Pedro Marronetti, the program director for gravitational physics at the National Science Foundation (NSF) and Lousto’s partner on the project. “The RIT group has performed the world’s most advanced simulations in this area, and each of them takes us closer to understanding observations that gravitational-wave detectors will provide in the near future.”

To run these simulations, Lousto and Marronetti once again turned to TACC: this time, its Frontera system. Frontera’s 8,008 Intel Xeon-based nodes deliver 23.5 Linpack petaflops of computing power, placing it eighth on the most recent Top500 list of the world’s most powerful supercomputers.

“Frontera was the perfect tool for the job,” Lousto said. “Our problem requires high performance processors, communication, and memory, and Frontera has all three.”

Using Frontera, the researchers simulated the collision – including the gravitational waves as they would be observed on Earth.

“These merged black holes can have speeds much larger than previously known,” Lousto said. “They can travel at 5,000 kilometers per second. They kick out from a galaxy and wander around the universe. That’s another interesting prediction.”

Next, the researchers are looking ahead to further simulations – including 11 more iterations of the current simulation.

To read the reporting by TACC’s Aaron Dubrow, click here.