Scientists unveil ‘most accurate virtual representation of the universe’

Researchers have created what they describe as the “largest and most accurate computer simulation to date” of our section of the universe.

Scientists created the simulations, from the Big Bang to the present, using a supercomputer to recreate the entire evolution of the cosmos.

By using advanced statistical techniques, the simulations are conditioned to reproduce our specific patch of universe, therefore containing the present day structures in the vicinity of our own galaxy that astronomers have observed for decades.

This means that the familiar structures within our local universe, such as the Virgo, Coma and Perseus clusters of galaxies, the Great Wall, have been reproduced in the simulation.

The Local Environment simulation
At the very centre of the simulation (and our own universe) is the Milky Way galaxy, and our nearest massive neighbour, the Andromeda galaxy (known as M31) (Durham University/PA)

At the centre of the simulation is a pair of galaxies – the virtual counterparts of our own Milky Way and the Andromeda galaxy.

During their research, the scientists found that our local patch of the universe may be unusual as the simulation predicted a lower number of galaxies than found in an average region of the universe due to a local large-scale underdensity of dark matter.

While the level of this underdensity is not considered to be a challenge to the standard model of cosmology, it could have consequences for how we interpret information from observed galaxy surveys.

The simulation, named Sibelius-Dark, is part of the Simulations Beyond the Local Universe (Sibelius) project.

It covers a volume up to a distance of 600 million light years from Earth and is represented by more than 130 billion simulated particles, requiring many thousands of computers working in tandem over several weeks and producing more than one petabyte of data.

The simulation was performed on the DiRAC COSmology MAchine (Cosma) operated by the Institute for Computational Cosmology at Durham University.

The researchers consisted of people across the world, including from Durham University, and were led by the University of Helsinki.

The findings have been published on arXiv.org and as a pre-print in the Monthly Notices of the Royal Astronomical Society journal.

Equatorial Coordinate system
Here the researchers show how the sky would look to us if we could see dark matter, the underlying skeletal structure of the universe – each projection is a shell of virtual universe at six ever increasing distances (Durham University/PA)

Professor Carlos Frenk, Ogden professor of fundamental physics at the Institute for Computational Cosmology at Durham University, said: “It is immensely exciting to see the familiar structures that we know exist around us emerge from a computer calculation.

“The simulations simply reveal the consequences of the laws of physics acting on the dark matter and cosmic gas throughout the 13.7 billion years that our universe has been around.

“The fact that we have been able to reproduce these familiar structures provides impressive support for the standard Cold Dark Matter model and tells us that we are on the right track to understand the evolution of the entire universe.”

Former Durham PhD student Dr Stuart McAlpine, who is now a postdoctoral researcher at the University of Helsinki, said: “By simulating our universe, as we see it, we are one step closer to understanding the nature of our cosmos.

“These simulations show that the current leading theory of cosmology, the Cold Dark Matter model, can produce all the galaxies we see in our local habitat, an essential benchmark for simulations of this kind to pass.

“This project provides an important bridge between decades of theory and astronomical observations.”

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