The DESI Legacy Imaging Surveys team released a 5.6-trillion-pixel map of nearly 4 billion celestial objects, the most comprehensive 2D map of the sky yet.
The DESI Legacy Imaging Surveys team has released the largest-ever 2D color map of the universe. The 5.6-trillion-pixel map contains nearly 4 billion celestial objects, primarily stars and galaxies, and the data is freely available for anyone to use and explore through the Legacy Survey Sky Viewer.
Among the nearly 4 billion objects captured is the galaxy Messier 96, a spiral galaxy roughly 35 million light-years from Earth, imaged using the 570-megapixel, Department of Energy-fabricated Dark Energy Camera (DECam) mounted on the National Science Foundation’s Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, a program of NSF NOIRLab.
Astronomers and citizen scientists alike can explore the map or combine it with their own observations to deepen understanding of the universe. Researchers can search for rare phenomena such as gravitational lenses, observe fleeting events like supernovae, and investigate two of physics’ biggest open questions: dark matter, the invisible substance that accounts for most of the mass in the universe, and dark energy, the force believed to be driving the universe’s accelerating expansion.
A Foundational Tool for Astronomy
The new map builds on earlier versions from the DESI Legacy Imaging Surveys, which have already proved invaluable to the field — more than 1,800 science papers referencing Legacy Surveys data have been published to date. “It’s part of the fabric of astronomy research now,” said David Schlegel, a co-lead of the Legacy Surveys and a scientist at the Department of Energy’s Lawrence Berkeley National Laboratory. “When you’re working with astronomical objects today, you often start by pulling up the Legacy Imaging Viewer to see what you’re looking at.”
The map covers roughly 75% of the sky in visible and near-infrared light, offering a deep view of the extragalactic universe unobstructed by the dust and stars of our own Milky Way. Researchers expect it to remain the most comprehensive 2D map of the universe for years to come.
More than 160 scientists contributed to data collection for the project, with a team of 20 producing the final released dataset. It was built by combining 263,407 telescope exposures from three ground-based sky surveys — the Dark Energy Camera Legacy Survey (DECaLS) at Cerro Tololo Inter-American Observatory, the Mayall z-band Legacy Survey (MzLS) at Kitt Peak National Observatory, and the Beijing-Arizona Sky Survey (BASS) at the University of Arizona’s Steward Observatory — supplemented by years of data from NASA’s Wide-field Infrared Survey Explorer (WISE) satellite mission and additional public data.
“For our team, these data are fundamental to our investigation of the expansion history of the universe and the formation of our galaxy,” said Arjun Dey, co-lead of the Legacy Surveys and an astronomer at NSF NOIRLab. “But the skies belong to everyone, and this survey gives everyone the chance to explore the sky and marvel at its wonders.”
Here Be Galaxies
The DESI Legacy Imaging Surveys were originally conducted to prepare for the Dark Energy Spectroscopic Instrument (DESI) survey. The 2D map functions as a deep photograph of the sky, recording where galaxies and stars appear and how bright they are — a crucial step that lets DESI select objects and measure their light across different wavelengths to determine their distances, building what is now the largest high-resolution 3D map ever made. By studying how galaxies clustered at different ages of the universe, scientists can track how dark energy has behaved over time.
In April 2026, DESI completed its original five-year survey ahead of schedule and with far more objects than expected. Early results have shown surprising hints that dark energy’s impact may be weakening over time, a potential paradigm shift that could reshape predictions about the universe’s ultimate fate. DESI expects to publish improved results using its first five years of data in 2027 and is continuing observations into 2028.
DESI proved so efficient at observing galaxies that the Legacy Surveys map itself needed to expand to keep up. “It became clear we might run out of galaxies to look at and run out of sky, and we better start doing something about that,” Schlegel said. The new Legacy Surveys map has been used to select DESI targets since June 2026 and will guide the telescope’s operations in the years ahead.
Computing the Cosmos
Merging hundreds of thousands of images taken across 2,285 nights, each with its own unique atmospheric and telescope conditions, was a massive computational undertaking. It took roughly a year to develop the necessary computer code and eight weeks to process all the images using the Perlmutter supercomputer at the National Energy Research Scientific Computing Center (NERSC) at Berkeley Lab.
Beyond supporting DESI, the Legacy Surveys are expected to serve as a foundational reference for the next generation of telescopes. As new observatories such as the NSF-DOE Vera C. Rubin Observatory and NASA’s Nancy Grace Roman Space Telescope come online, researchers will be able to compare their observations against one of the deepest and most comprehensive views of the sky ever assembled. The Legacy Surveys data will also help train artificial intelligence tools to analyze petabytes of astronomical data and accelerate future discoveries, and will be among the datasets used in an astrophysics pilot project within the American Science Cloud, part of the Department of Energy’s Genesis Mission.