Long before there were stars to read by, the universe was a dense, glowing fog, and somewhere in those first two billion years its matter began gathering into a vast lattice of filaments that would later seed galaxies. Scientists have now rebuilt that early stretch of cosmic history in a computer model called Lumina, run on the Frontier supercomputer, following both the invisible dark matter and the gas that slowly cleared into transparency. It is an attempt to hold our theories of creation up against the faint, ancient light that the James Webb Space Telescope is now collecting, so that the s
Supercomputer 'Lumina' Simulates the Universe's First Two Billion Years and Its Cosmic Web
The next best thing to time travel
Mark
So what is Lumina, in plain terms?
Mimi
A simulation of the universe's first two billion years, run on 15,000 GPUs on the Frontier supercomputer in Tennessee. It shows dark matter, gas temperature and the cosmic web.
Mark
Why does the scale matter?
Mimi
The cube is 1.5 billion light years across, yet it still resolves individual galaxies and black holes. Usually you trade one for the other.
Mark
And the fog clearing?
Mimi
Radiation stripped electrons from atoms, and transparent bubbles of hydrogen and helium opened up so starlight could travel freely. Aaron Smith says they can follow both hydrogen and helium across that whole volume.
Luke
Let me slow us down. Is the video what the universe looked like?
Mimi
It's what the best estimates say it looked like at 1.5 billion years. It's a model, not a photograph.
Luke
Right. And has the model been confirmed by JWST?
Mimi
The reporting says astronomers have compared it with JWST observations and want to test their understanding. It doesn't say how well the two match.
Luke
That's the gap. The result so far is the simulation itself; the verdict is still to come.
Mark
So what do we watch for?
Mimi
Whether Lumina's predictions hold up against the ancient galaxies JWST sees.
The Pulse
- A fog-filled young universe is being mapped across an enormous stretch of space, and the stakes are whether theories of early cosmic structure can survive contact with real observations.
- Frontier's 15,000 graphics processors are churning through a model vast enough to hold the cosmic web yet fine enough to resolve individual galaxies and black holes.
- Researchers are tracking the moment hydrogen and helium cleared into transparent bubbles, freeing starlight to shine across the universe for the first time.
- The team is now setting Lumina's predictions against JWST's light from ancient galaxies, moving the work from simulation toward verification.
Long before there were stars to read by, the universe was a dense, glowing fog, and somewhere in those first two billion years its matter began gathering into a vast lattice of filaments that would later seed galaxies. Scientists have now rebuilt that early stretch of cosmic history in a computer model called Lumina, run on the Frontier supercomputer, following both the invisible dark matter and the gas that slowly cleared into transparency. It is an attempt to hold our theories of creation up against the faint, ancient light that the James Webb Space Telescope is now collecting, so that the story of how the first structures came to be can be checked against the sky itself.
The video begins with a cube of space 1.5 billion light years on each side, a bright web of dark matter and glowing gas crisscrossing the darkness. It shows the universe as it looked about 1.5 billion years after the Big Bang, and the camera slowly moves inward toward a single galaxy buried in the lattice.
The footage comes from Lumina, a simulation built by scientists at the Center for Astrophysics, a collaboration between the Smithsonian Astrophysical Observatory and Harvard College Observatory. Its purpose is to render the cosmic web across the universe's first two billion years in more detail than any model before it.
Running it took enormous computing power. Lumina used 15,000 graphics processing units on Frontier, a supercomputer housed at the Oak Ridge Leadership Computing Facility in Tennessee. That allowed the team to capture a vast region of space while still modeling the birth of individual galaxies and black holes.
The model also tracks a turning point in cosmic history, when a thick fog of gas gave way to transparent hydrogen and helium and starlight could finally travel freely. Aaron Smith of the University of Texas at Dallas, a co-author, said this is the first time researchers can follow that change across such a huge volume while still resolving the galaxies driving it.
The real test lies ahead. Astronomers want to compare Lumina with images from the James Webb Space Telescope of galaxies whose light has taken billions of years to arrive. Oliver Zier, the lead author, described years of effort with many setbacks, and said it has been deeply rewarding to watch predictions take shape. The next step, already underway, is to see whether those predictions match what the ancient galaxies reveal.
The video opens on a cube of space, 1.5 billion light years along each edge, which is about 15,000 times the width of the Milky Way's disk. Inside it, a bright web of vast strands, made of dark matter and glowing gas, crisscrosses the dark. By the best current estimates, this is the universe as it looked 1.5 billion years after the Big Bang.
The footage comes from a simulation named Lumina, built by scientists at the Center for Astrophysics, a collaboration between the Smithsonian Astrophysical Observatory and Harvard College Observatory. It is described as the most detailed model yet of how the universe evolved over its first two billion years, and it renders in fine detail the structure known as the cosmic web.
As the video moves inward, it cycles through filters. One shows the density of dark matter, another the temperature of the gas clouds. The camera finally settles on a single galaxy buried within the web. A still image from the run shows a region of the early universe 600 million light years across, where fine filaments of dark matter thread through clouds of gas colored orange and yellow according to their speed.
The computing behind it is considerable. Lumina ran on 15,000 graphics processing units on Frontier, one of the fastest supercomputers in the world, housed at the Oak Ridge Leadership Computing Facility in Tennessee. That capacity let the team build a model large enough to capture a huge stretch of space while still detailed enough to simulate the formation of individual galaxies and black holes.
The simulation also follows a major transition in cosmic history. The young universe was filled with a thick fog of gas. Radiation stripped electrons from their atoms, and large transparent bubbles of hydrogen and helium opened up, allowing starlight to penetrate the gas and shine freely across the universe.
Aaron Smith of the University of Texas at Dallas, another author of the study, said that for the first time researchers can follow both hydrogen and helium changing into their modern form across such an enormous volume, while still resolving the galaxies and other luminous objects driving that change.
The point of the exercise is comparison. Astronomers have set the simulation against observations from the James Webb Space Telescope of ancient galaxies, whose light has traveled for billions of years to reach us. They want to test their understanding of how galaxies, and even larger structures, formed.
Oliver Zier, lead author of the study, published in the Monthly Notices of the Royal Astronomical Society, said JWST has made the early universe an exciting new frontier. Understanding what the telescope sees, he said, requires turning theories into detailed predictions. After several years of work, with plenty of ups and downs, he called it incredibly rewarding to watch those predictions come to life.
The next step is the one already underway: checking Lumina's predictions against what JWST finds in those ancient galaxies.
Notable Quotes
For the first time we can follow both hydrogen and helium changing into their modern form across such an enormous volume, while still resolving the galaxies driving that transformation.— Aaron Smith, University of Texas at Dallas
To understand what JWST shows us, theories must be translated into detailed predictions.— Oliver Zier, lead author (paraphrased)
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