Illustris Collaboration
This large-scale picture of the universe, created by Illustris, shows clouds of cold gas where stars are formed (green), warmer gas (blue), and hot regions around galaxies (red).
A new simulation of the evolution of the universe is one of the most accurate ever created. The model, developed by a team of scientists led by Mark Vogelsberger at the Massachusetts Institute of Technology, traces the history of the universe from shortly after its birth to present day and captures both the large scale of universe and the detail of individual galaxies better than previous attempts.
The details were published in a paper on May 7 in the journal Nature.
Modeling Challenges
Creating a realistic model of the universe has long been a struggle for cosmologists. One problem is that the universe is mostly composed of dark matter and dark energy, two mysterious substances that scientists can't directly observe or measure, but that are thought to give all the stars and galaxies in our universe their underlying structure. Only 5% of the universe is made up of matter we can see.
Generating an accurate picture of something we don't yet fully understand is challenging for obvious reasons, but cosmologists have found that modeling visible matter is just as, if not more, difficult. That's because a simulation that captures the evolution of the universe from its early history to present day requires scientists to use a huge range of scales - starting from the very small physical scales that describe the evolution of gas and individual stars to the larger scales that are needed to show the formation and distribution of galaxies.
Nature
The simulation models both the stars and the galaxies that we can see and the dark matter that we can't see - but that makes up 95% of the universe.
The universe was created during the Big Bang 13.8 billion years ago. But there are many questions about how galaxies and stars evolved between then and now. That's why scientists use computer models to fill in the billion of years between the birth of the universe and what we observe today.
Nature
The universe burst into existence 13.8 billion years ago in the Big Bang. But scientists are still trying to understand how cosmic features evolved between then and present day.
A Virtual Universe
Now, using a simulation named Illustris, Vogelsberger and his team were able to model both large- and small-scale features of the universe on a time scale that starts 12 million years after the Big Bang (when the universe was very young) and continues for the next 13 billion years.
The new simulation models a volume of space almost 350 million light-years across. This is a large enough piece to be representative of the whole universe, but detailed enough to look at the composition of individual galaxies. No team has done this before.
Nature
Illustris captured the huge scales of the universe.
On top of that, the simulation reproduces the distribution of different elements, including the hydrogen and helium that made up the early universe and the heavier elements required for planet formation.
The scientists were also able to model many different types of galaxies (more than 40,000 are modeled in the simulation), including elliptical galaxies and disk galaxies like our Milky Way.
"Images of galaxies from the simulation are also impressively realistic, an accomplishment that has previously been possible only for simulation of individual galaxies," Michael Boylan-Kolchin, an astronomer at the University of Maryland, said in a news article published by Nature.
Images of the simulated galaxy population "appear strikingly similar" to real images of galaxies observed by the Hubble Space Telescope "in terms of number density, colors, sizes, and morphologies," the authors wrote in their paper.
The simulation is not perfect, the study noted, but it "does represent a significant step forward in modeling galaxy formation." Check out the video: