A fake universe is giving some astronomers pause, because it looks too much like the real one.
Scientists behind the COLIBRE virtual universes say their new audiovisual simulation offers their best picture yet of how the cosmos evolved from the first billion years after the Big Bang to today. Using the standard model of cosmology, the project models the dynamics of cold galactic dust and gas, the raw material that forms stars.
The team says the simulation comes closer than earlier efforts to matching what the James Webb Space Telescope has been seeing in the early universe. That, in turn, supports the standard model of cosmology, also known as the Lambda Cold Dark Matter, or LCDM, model.
“It is exhilarating to see ‘galaxies’ come out of our computer that look indistinguishable from the real thing and share many of the properties that astronomers measure in real data, such as their number, luminosities, colors and sizes,” COLIBRE team member Carlos Frenk said in a statement.
“I like to tease my observer colleagues by asking, ‘Which galaxy catalogue do you think these images came from?’ What is most remarkable is that we are able to produce this synthetic universe purely by solving the relevant equations of physics in the expanding universe.”
The simulation runs on the COSMA8 supercomputer at Durham University. According to the researchers, it has cleared a hurdle that had blocked other large cosmic simulations, accurately modelling cold gas.
That matters because stars form when cold gas and dust collapse under their own gravity. To simulate star formation properly, scientists need to track how cold gas moves.
COLIBRE also simulated small dust grains and their role in helping form hydrogen molecules. The team said those grains also block ultraviolet light that would otherwise stop gas from cooling and forming stars.
“Much of the gas inside real galaxies is cold and dusty, but most previous large simulations had to ignore this,” COLIBRE leader Joop Schaye, of Leiden University in the Netherlands, said in the statement.
“With COLIBRE, we finally bring these essential components into the picture.”
The researchers say that extra computing power helped them build a synthetic universe that closely resembles JWST observations of the early cosmos. The result is detailed enough that some astronomers are doing double-takes when they look at the images.
Even so, the simulation does not answer every question raised by JWST.
One of the remaining puzzles involves the so-called little red dots that JWST has found in large numbers during a particular period in cosmic history. The source text says these objects appear in vast numbers 600 million years after the Big Bang and disappear after the universe is around 1.5 billion years old.
The article says one possible explanation is that the objects are heavy black hole seeds. But the COLIBRE virtual universes have not yet accounted for them.
Most of the simulations were completed in 2025, though some are still running. The researchers say the data already produced will take years to analyse.
The project also includes sound. James Trayford, of the University of Portsmouth in the United Kingdom, led development of COLIBRE’s dust model and the sonification of its visualisations.
“We’re excited not just about the science, but also about creating new ways to explore it,” Trayford said in the statement.
“These tools could provide new insights, make our field more accessible, and help us build intuition for how galaxies grow and evolve.”
The COLIBRE research was published on Monday, April 13, in the journal Monthly Notices of the Royal Astronomical Society.
