Illustris computer simulation creates the first realistic virtual universe

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Illustris simulation still frame centered on the most massive galaxy cluster existing today, with dark matter shown as blue-purple filaments and bubbles of red, orange and white indicating gas being blasted outward by supernovae or jets from supermassive black holes (Image: Illustris Collaboration)

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As you might expect, the scale and complexities of the underlying physics means creating a realistic virtual universe would require some hefty computing power. A team of astronomers is claiming to have achieved this impressive feat using a computer simulation called "Illustris," which took five years to program and, for the first time, can recreate the evolution of the Universe in high fidelity.

Whereas using the average desktop PC to carry out the calculations required to simulate everything from the expansion of the Universe, the gravitational pull of matter onto itself, the motion or "hydrodynamics" of cosmic gas, as well as the formation of stars and black holes would have taken more than 2,000 years, the project, which was a collaboration involving researchers from several institutions, used a total of 8,000 CPUs running in parallel to cut the required "run time" to three months.

Starting a brief (in cosmological terms) 12 million years after the Big Bang, the computer simulation recreates 13 billion years of cosmic evolution through to the current day in a cube of simulated space measuring 350-million light years on a side. The astronomers counted over 41,000 galaxies in the current-day cube, including what they say is a realistic mix of spiral galaxies like the Milky Way and football-shaped elliptical galaxies. The simulation includes both normal and dark matter using 12 billion 3D "pixels," or resolution elements.

It also reproduced the Universe on both small and large scales, from the chemistries of individual galaxies, up to large-scale structures, such as galaxy clusters and the bubbles and voids of the cosmic web. The astronomers say this is an improvement on earlier simulations that were limited in resolution or forced to focus on a small portion of the Universe, and also ran into difficulties modeling complex feedback from star formation, supernova explosions and supermassive black holes.

The team says that although telescopes such as Hubble can give us a window back in time to the early universe by looking farther away, they are unable to follow the evolution of a single galaxy over time. That's where Illustris comes in.

"Illustris is like a time machine," says co-author of the study, Shy Genel of the Harvard-Smithsonian Center for Astrophysics (CfA). "We can go forward and backward in time. We can pause the simulation and zoom into a single galaxy or galaxy cluster to see what's really going on."

The team's study is published in the journal Nature, and a compilation of some of the movies showing the simulation can be seen in the video below.

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