Largest Cosmic Map Completed: Legacy Surveys Reveal 11 Billion Years of History

After a five-year data-collection effort that built on more than a decade of prior work, the Legacy Surveys have produced the most extensive astronomical map to date. Over 160 scientists contributed to the survey, and the data have already underpinned roughly 1,800 published papers. The full five-year dataset will be analyzed in a study slated for release in 2027, promising an unprecedented view of the universe’s past and present.

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Earlier this year, researchers from the Dark Energy Spectroscopic Instrument (DESI) released a map charting the distances of 47 million galaxies and quasars, reconstructing about 11 billion years of cosmic history. That work highlighted the role of dark energy in driving universal expansion and suggested, from the first three years of DESI data combined with supernovae and cosmic-microwave-background observations, that dark energy may be weakening over time. The new Legacy Survey map expands this foundation, offering a reference point for forthcoming projects such as NASA’s Nancy Grace Roman Space Telescope.

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The survey’s petabyte-scale data set captures billions of celestial objects across the sky. Researchers plan to apply artificial-intelligence tools to accelerate analysis, aiming to uncover additional structures and phenomena hidden within the massive archive.

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• “Explorations of our universe always start with images of the night sky,” — Arjun Day

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