A six-year survey of 669 million galaxies has revealed insights into dark energya mysterious phenomenon driving the accelerating expansion of the universe.
The survey paints a complicated picture of our understanding of the universe, showing that the two main theories of cosmology are both equally suited to new observations of the universe’s expansion. But both theories still fall short of explaining why matter clumps together in the universe the way it does, suggesting more work needs to be done.
“These results from the Dark Energy Survey shed new light on our understanding of the universe and its expansion,” Queen RameikaDeputy Director of the Office of High Energy Physics of the US Department of Energy, said Mr declaration. “They show how long-term investment in research and combining different types of analysis can provide insight into some of the biggest mysteries of the universe.”
Expanding our knowledge
Dark energy is thought to make up about 70% of the total energy in the universe, but astronomers still know very little about its true nature. Scientists proposed the concept to explain observations that suggest the universe is expanding at an ever-accelerating rate. DES is one of several collaborations developed to study this phenomenon in more detail.
In a new paper submitted to the preprint server arXiv On Jan. 21, DES scientists used four kinds of markers to probe the expansion of the universe: baryonic acoustic oscillations, or fluctuations in the density of normal matter throughout the universe; Type Ia supernovae, stellar explosions that can help scientists measure the distance of cosmic objects; galaxy clusters; and weak gravitational lensing, which occurs when a cluster of galaxies warps space-time and distorts the apparent shapes of objects behind it. A series of 18 supporting papers elaborate on the findings.
Overall, the data and analysis are consistent with previous studies of dark energy, although the new work places tighter constraints on models of how the universe behaves. The data mostly agree with the Standard Model of cosmology, in which the dark energy density is constant. The data also fit a related model in which the dark energy density changes over time, but did not fit any better than the Standard Model.
“It’s an incredible feeling to see these results based on all the data and with all four probes that DES has planned,” study co-author Yuanyuan Zhangastronomer at the National Science Foundation’s NOIRLab, which manages the telescope, said in a statement. “It was something I would only dare to dream of when DES started collecting data, and now the dream has become a reality.”
Despite the relatively good fit between the data and the standard model, some questions remain. The galaxy clustering pattern still does not exactly match the predictions from the Standard Model, but it is not different enough to conclude that the Standard Model is wrong, the team added.
Nevertheless, DES researchers will continue to test this and other models of dark energy in conjunction with Vera C. Rubin Observatory in Chile to further refine our understanding of the mysterious phenomenon.
“Rubin’s unprecedented survey of the southern sky will enable new tests of gravity and shed light on dark energy,” Chris DavisNSF program director for NOIRLab, said in a statement.
DES Collaboration, TMC Abbott et al. (January 21, 2026). Dark Energy Survey Year 6 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing. arXiv.org. https://arxiv.org/abs/2601.14559
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