Dark energy remains unresolved after final Dark Energy Survey results

The six-year Dark Energy Survey published its final results after observing 669 million galaxies and mapping one-eighth of the sky; the findings tighten measurements but do not settle whether dark energy is constant or evolving.

Scientists published the final results from the six-year Dark Energy Survey, completing an extensive map of the sky and refining measurements related to dark energy. The project involved more than 400 researchers and used the DECam camera built by Fermilab on a telescope in Chile. Over 758 nights the team recorded data on 669 million galaxies, covering an eighth of the sky. The new results reduce uncertainties and improve methods, but they do not resolve the fundamental nature of dark energy. Key facts: - The Dark Energy Survey was a six-year international collaboration involving over 400 scientists. - Observations occurred across 758 nights with DECam and captured data on 669 million galaxies across one-eighth of the sky. - The survey's analyses produce tighter constraints that fall between a constant dark energy density and models in which dark energy evolves over time. - Researchers developed advanced gravitational lensing methods and produced a detailed reconstruction of matter distribution across the universe. - Teams report that the survey's data and techniques are informing next-generation projects, including the Ruben Observatory, the Euclid satellite, and the Roman Space Telescope. - Project leaders characterize the release as a refinement of understanding and a transfer of tools and experience to future experiments. Summary: The Dark Energy Survey's final release refines measurements and advances analysis methods but does not answer what dark energy is. Undetermined at this time, the question will be probed further by upcoming observatories and space missions that build on these results.