Rahul Somvanshi
The Euclid Consortium has just released Flagship 2, the most extensive simulation of the universe ever created. This digital model maps an astonishing 3.4 billion galaxies and tracks the gravitational interactions of more than 4 trillion particles, giving scientists an unprecedented virtual universe to study.
The simulation was built using an algorithm developed by astrophysicist Joachim Stadel from the University of Zurich. In 2019, the calculation was run on Piz Daint, then the third most powerful supercomputer in the world, using more than 80% of its total capacity.
“It was a huge challenge to simulate such a large portion of the universe at this resolution in a single calculation,” Stadel explains.
What makes Flagship 2 remarkable is not just its size but its detail. Each of the 3.4 billion galaxies comes with 400 modeled properties including brightness, position, velocity, and shape. The simulation even identified 16 billion dark matter “haloes” – gravitational structures where galaxies form – extending out to 18.6 billion light-years from Earth.
The purpose behind this massive digital universe is practical. The European Space Agency’s Euclid space telescope, launched in July 2023, is currently mapping one-third of the sky, producing enormous amounts of data. Flagship 2 helps scientists prepare for analyzing this real-world data.
“These simulations are crucial for preparing the analysis of Euclid’s data,” says Julian Adamek, who collaborated on the project. Euclid produces so much information that automated systems must process it, and those systems need testing before the real data arrives.
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Flagship 2 is built on the standard cosmological model – our current understanding of how the universe works. But the researchers expect Euclid’s actual observations might reveal surprises.
“We already see indications of cracks in the standard model,” Stadel notes. The mission might help answer fundamental questions about dark energy, the mysterious force driving the universe’s expansion.
Euclid’s observations can look back up to 10 billion years in cosmic history. “We can see how the universe expanded at that time and measure whether this constant really remained constant,” explains Adamek.
The catalog was developed by an international team of eight institutions within the Euclid Consortium, led by the Institute of Space Sciences (ICE-CSIC) and the Port d’Informació Científica (PIC). It’s now publicly available on the CosmoHub platform for researchers worldwide to access.
Jorge Carretero, researcher at PIC, highlights: “This is a huge step for the scientific community, since it is now accessible for everyone. It can have many different scientific applications beyond the context of the Euclid mission.”
Euclid’s first observational data was released in March 2025, representing only a small portion of the mission’s complete dataset. The next major release is scheduled for October 21, 2026. Meanwhile, Flagship 2 will help scientists refine their tools and prepare for new discoveries that may reshape our understanding of the cosmos.
