Scientists unveil Flagship 2, the largest universe simulation ever with 3.4 billion galaxies

Euclid Flagship 2 was trained on Piz Daint, the third most powerful supercomputer in the world.

New Delhi | Updated: September 30, 2025 07:06 PM IST

3 min read

Image extracted from the Euclid Flagship universe simulations catalogue. Each dot represents a galaxy: blue points mark galaxies at the centers of dark matter clumps, while red points denote satellites within them. (Image Source: Euclid Consortium)

Euclid Consortium, the international group that manages the European Space Agency’s Euclid space telescope, has published the largest ever simulation of the universe. Called Flagship 2, the simulation mapped 3.4 billion galaxies and tracks the gravitational interaction of more than 4 trillion particles.

Based on an algorithm designed by the astrophysicist Joachim Stadel from the University of Zurich, the simulation was run on Piz Daint, the third most powerful supercomputer in the world. The calculation was carried out back in 2019 and required more than 80 per cent of the supercomputer’s total capacity.

In a statement, astrophysicist Julian Adamek, who worked on the project, said that “these simulations are crucial for preparing the analysis of Euclid’s data.” For those not in the loop, the Euclid space telescope has been finding and mapping billions of galaxies across the universe and studying the distribution of dark energy and dark matter since 2023.

The Flagship 2 mock simulation is based on the standard cosmological model and uses currently available knowledge about the composition and evolution of the universe. And while both Stadel and Adamek say that they expect Euclid’s observations to be in line with the current model, researchers are excited about seeing unexpected discoveries.

Stadel says that they are already seeing indications of cracks in the standard model, to which Adamek added, “It will be exciting to see whether the model holds up against Euclid’s high precision data – or whether we uncover signs of new shortcomings.” The simulation might also help us learn more about the nature of dark energy, a constant that explains the expansion of the universe. “We can see how the Universe expanded at that time and measure whether this constant really remained constant”, says Adamek.

To give you a quick recap, Euclid is the most detailed map of the cosmos ever made, not only in scale but also in precision. Spectroscopic measurements from the model. Euclid’s data allows scientists to look back up to 10 billion years in the universe’s history, but it is still unclear if it will help us find answers. However, Stadel believes the model will help us take a step forward in understanding the “phenomena that cannot be explained within the current theoretical framework” and there are “chances of finding unexpected or rare objects.”

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