Astrophysicists have used the mighty weight of Germany’s fastest computer to create the most detailed simulation of the universe ever seen.
Called Illustris: The Next Generation, or IllustrisTNG, the simulation models a cube-shaped universe, somewhat smaller than our own but with many of the features experts have seen or believe exist.
Building on the original Illustris simulation, which measured 350 million light years per side, the IllustrisTNG follows the formation of millions of galaxies in a representative region of a universe with almost one billion light years per side.
The cosmic web of gas and dark matter simulated by IllustrisTNG shows galaxies forming that are similar to real galaxies in shape and size. For the first time, such hydrodynamic simulations could “directly compute the detailed clustering pattern of galaxies in space” and give a much more realistic view of the distant universe than observational data – such as the data provided by the powerful Sloan Digital Sky Survey – can reveal.
“When we observe galaxies using a telescope, we can only measure certain quantities,” said Shy Genel, an associate research scientist at the Flatiron Institute’s Center for Computational Astrophysics. “With the simulation, we can track all the properties for all these galaxies. And not just how the galaxy looks now, but its entire formation history.”
Mapping how galaxies evolve could unlock secrets of what our own Milky Way galaxy might have been like when the Earth formed, and how our galaxy could change in the future.
The simulations also predict how the cosmic web changes over time, especially in relation to the dark matter. “It is particularly fascinating that we can accurately predict the influence of supermassive black holes on the distribution of matter out to large scales,” said Volker Springel, principal investigator at the Heidelberg Institute for Theoretical Studies. “This is crucial for reliably interpreting forthcoming cosmological measurements.”
For the project, researchers from across five institutions developed a particularly powerful version of code and used it on the Hazel Hen machine, Germany’s fastest mainframe computer, at the High Performance Computing Center Stuttgart.
These institutions included the Max Planck Institutes for Astronomy, and Astrophysics, Harvard University, the Massachusetts Institute of Technology and the Flatiron Institute’s Center for Computational Astrophysics, and their findings are published in three papers in the Monthly Notices of the Royal Astronomical Society.
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The teams used more than 24,000 processors over the course of two months to generate more than 500 terabytes of data. “Analysing this huge mountain of data will keep us busy for years to come, and it promises many exciting new insights into different astrophysical processes,” explained Springel.
It could, for example, offer fresh insights into how black holes interact with and change the distribution of dark matter, how heavy elements are produced and distributed, and where magnetic fields come from.
Using the data, Dylan Nelson, a researcher at MPA, has already been able to demonstrate the impact of black holes on galaxies. Star-forming galaxies shine brightly in the blue light of their young stars until a sudden evolutionary shift stops the stars from forming, meaning the galaxy becomes dominated by old, red stars, and joins a graveyard full of old and dead galaxies.
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“The only physical entity capable of extinguishing the star formation in our large elliptical galaxies are the supermassive black holes at their centres,” explained Nelson. “The ultrafast outflows of these gravity traps reach velocities up to 10% of the speed of light and affect giant stellar systems that are billions of times larger than the comparably small black hole itself.”
Image: IllustrisTNG collaboration
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