Dark Energy Survey Scientists Release Evaluation of All Six Years of Survey Data

Four strategies for learning darkish power come collectively in a single experiment for the primary time

22 January 2026

The Dark Energy Survey Collaboration collected data on tons of of thousands and thousands of galaxies throughout the Universe utilizing the U.S. Department of Energy-fabricated Dark Energy Camera, mounted on the U.S. National Science Foundation Víctor M. Blanco 4-meter Telescope at CTIO, a Program of NSF NOIRLab. Their accomplished evaluation combines all six years of information for the primary time and yields constraints on the Universe’s enlargement historical past which might be twice as tight as previous analyses.

The Dark Energy Survey (DES) is a world, collaborative effort to map tons of of thousands and thousands of galaxies, detect hundreds of supernovae, and discover patterns of cosmic construction that can assist reveal the character of the mysterious dark energy that’s accelerating the enlargement of our Universe.

From 2013 to 2019, the DES Collaboration carried out a deep, wide-area survey of the sky utilizing the 570-megapixel DOE-fabricated Dark Energy Camera (DECam), mounted on the NSF Víctor M. Blanco 4-meter Telescope at NSF Cerro Tololo Inter-American Observatory (CTIO) in Chile. For 758 nights over six years, the DES Collaboration recorded data from 669 million galaxies which might be billions of light-years from Earth, masking an eighth of the sky.

Today, the DES Collaboration is releasing outcomes that, for the primary time, mix all six years of information from weak lensing and galaxy clustering probes — two strategies for measuring the Universe’s enlargement historical past. The collaboration additionally presents the primary outcomes discovered by combining all 4 strategies of measuring the enlargement historical past of the Universe — baryon acoustic oscillations (BAO), Type-Ia supernovae, galaxy clusters, and weak gravitational lensing — as proposed on the inception of DES 25 years in the past. The paper, submitted to Physical Review D, represents a abstract of 18 supporting papers.

“It is an incredible feeling to see these results based on all the data, and with all four probes that DES had planned. This was something I would have only dared to dream about when DES started collecting data, and now the dream has come true,” says Yuanyuan Zhang, assistant astronomer at NSF NOIRLab and member of the DES Collaboration.

The evaluation yields new, tighter constraints that slim down the doable fashions for the way the Universe behaves. These constraints are greater than twice as robust as these from previous DES analyses whereas remaining in step with earlier DES outcomes.

“These results from the Dark Energy Survey shine new light on our understanding of the Universe and its expansion,” stated Regina Rameika, Associate Director for the Office of High Energy Physics within the DOE’s Office of Science (DOE/SC). “They demonstrate how long-term investment in research and combining multiple types of analysis can provide insight into some of the Universe’s biggest mysteries.”

The first clue for darkish power was uncovered a couple of century in the past when astronomers observed that distant galaxies gave the impression to be transferring away from us. In reality, the farther away a galaxy is, the quicker it recedes. This offered the primary key proof that the Universe is increasing. But because the Universe is permeated by gravity, a power that pulls matter collectively, astronomers anticipated the enlargement would decelerate over time.

Then, in 1998, two impartial groups of cosmologists used distant supernovae to find that the Universe’s enlargement is accelerating slightly than slowing. To clarify these observations, they proposed a brand new form of phenomenon that’s liable for driving the Universe’s accelerated enlargement: darkish power. Astrophysicists now imagine darkish power makes up about 70% of the mass-energy density of the Universe. Yet, we nonetheless know little or no about it. 

In the next years, scientists started devising experiments to check darkish power, together with DES. Today, DES is a world collaboration of over 400 astrophysicists and scientists from 35 establishments in seven nations led by DOE’s Fermi National Accelerator Laboratory.

For the most recent outcomes, DES scientists tremendously superior strategies utilizing weak lensing to robustly reconstruct the distribution of matter within the Universe. Weak lensing is the distortion of sunshine from distant galaxies as a result of gravity of intervening matter, like galaxy clusters. They did this by measuring the chance of two galaxies being a sure distance aside and the chance that also they are distorted equally by weak lensing. By reconstructing the matter distribution over six billion years of cosmic historical past, these measurements of weak lensing and galaxy distribution inform scientists how a lot darkish power and dark matter there’s at every second.

In this evaluation, DES examined two fashions of the Universe towards their knowledge. There is the presently accepted normal mannequin of cosmology — Lambda chilly darkish matter (ΛCDM) — during which the darkish power density is fixed. There can be an extended model, during which the darkish power density evolves over time — wCDM. 

DES discovered that their knowledge largely aligned with the usual mannequin of cosmology. Their knowledge additionally match the evolving darkish power mannequin, however no higher than they match the usual mannequin. 

However, one parameter remains to be off. Based on measurements of the early Universe, each the usual and evolving darkish power fashions predict how matter within the Universe clusters at later occasions. In earlier analyses, galaxy clustering was discovered to be totally different from what was predicted. When DES added the latest knowledge, that hole widened, however not but to the purpose of certainty that the usual mannequin of cosmology is inaccurate. The distinction endured even when DES mixed their knowledge with these of different experiments.

Next, DES will mix this work with the latest constraints from different darkish power experiments to analyze different gravity and darkish power fashions. This evaluation can be essential as a result of it paves the best way for the brand new NSF–DOE Vera C. Rubin Observatory, funded by the NSF and DOE/SC, and collectively operated by NSF NOIRLab and SLAC, to gather complementary knowledge throughout its decade-long Legacy Survey of Space and Time (LSST). LSST is a deep and huge survey that can catalog about 20 billion galaxies throughout your complete Southern Hemisphere sky. The knowledge could be mixed with these from surveys like DES to allow high-accuracy measurements of cosmological parameters that can additional refine our understanding of darkish power and the enlargement historical past of the Universe.

“DES has been transformative, and the NSF–DOE Vera C. Rubin Observatory will take us even further,” stated Chris Davis, NSF Program Director for NOIRLab. “Rubin’s unprecedented survey of the southern sky will enable new tests of gravity and shed light on dark energy.”

More data

This analysis is introduced in a paper titled “Dark Energy Survey Year 6 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing,” submitted to Physical Review D and appearing on arXiv.

These outcomes are introduced by the DES Collaboration.

NSF NOIRLab, the U.S. National Science Foundation heart for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) below a cooperative settlement with NSF and is headquartered in Tucson, Arizona. 

The scientific group is honored to have the chance to conduct astronomical analysis on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) group.

This work is supported partially by the U.S. Department of Energy Office of Science. The Dark Energy Survey is a collaboration of greater than 400 scientists from 26 establishments in seven nations. Funding for the DES Projects has been offered by the U.S. Department of Energy Office of Science, U.S. National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, ETH Zurich for Switzerland, National Center for Supercomputing Applications on the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics on the University of Chicago, Center for Cosmology and AstroParticle Physics at Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Ministério da Ciência e Tecnologia, Deutsche Forschungsgemeinschaft, and the collaborating institutions in the Dark Energy Survey.

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Contacts

Yuanyuan Zhang
DES Collaboration
NSF NOIRLab
Email: yuanyuan.zhang@noirlab.edu

Josie Fenske
Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

Tracy Marc
Media Relations Manager
Fermilab
Email: tracym@fnal.gov