This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In dark skies at night, distant starlight twinkles and speaks to vast cosmic histories almost as old as time itself. New data from instruments such as NASA's James Webb Space Telescope are helping astrophysicists probe deep cosmic mysteries, including the evolution of black holes and galaxies.
Using supercomputers to help make sense of the data, researchers from multiple institutions worked together to complete the largest cosmological hydrodynamic simulation, called ASTRID—a mind-boggling computational run that traces the evolution of the universe from its earliest times to the present. "The most important information about our recent study is that we've evolved the ASTRID simulation to z = 0, and that these data are available," said Yihao Zhou, a Ph.D. student in Carnegie Mellon University's (CMU) Department of Physics. Zhou and colleagues published their study in The Astrophysical Journal in March 2026.
The term "z" denotes the redshift of starlight, in which light shifts toward the red end as its source moves away from an observer. High redshift corresponds to greater distances and earlier periods in the universe's history, when the universe was expanding rapidly shortly after the Big Bang. Zhou's team started their cosmological simulations from z = 99, covering the "cosmic dawn" of the universe.
ASTRID traced 13.5 billion years of galactic structure and black hole evolution to z = 0, the present day. "We have this very large simulation and piece of the universe, which captures the growth of black holes from the time at which they were formed all the way to today, as well as the galaxies that form, also from a very early time," said study co-author and ASTRID principal investigator Tiziana Di Matteo, professor of physics and director of CMU's McWilliams Center for Cosmology & Astrophysics. Di Matteo made use of the Frontera supercomputer at the Texas Advanced Computing Center (TACC).
It gave the ASTRID team the computational power to model 166 billion particles across a volume of space 815 million light-years across, an enormous virtual laboratory for studying the universe. Furthermore, the researchers solved complex physical interactions, including gravity and hydrodynamics, for each time step, which necessitated building "gravity trees" to efficiently compute long- and short-range gravitational forces across billions of particles. "This is a very demanding process, and only large compute clusters like Frontera can do this," Zhou said.
The data input/output process for ASTRID was also computationally demanding, with each simulation snapshot totaling 30 terabytes. "TACC's Ranch archive system saved our ASTRID data," Zhou added. "The NSF has provided state-of-the-art resources in Frontera," Di Matteo said.
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