Astronomers Release Largest 2D Map of the Universe Featuring 4 Billion Objects

The DESI Legacy Imaging Surveys team has released the largest two-dimensional color map of the universe ever created. This massive dataset serves as a critical target selection tool for the Dark Energy Spectroscopic Instrument (DESI) as it works to construct a subsequent 3D map of the cosmos.

Led by Lawrence Berkeley National Laboratory and NSF NOIRLab, the project produced an atlas containing 5.6 trillion pixels. The map catalogs nearly 4 billion celestial objects—primarily stars and galaxies—across approximately 75% of the sky. To achieve this scale, the team combined 263,407 exposures from three distinct ground-based programs: the Dark Energy Camera Legacy Survey (DECaLS) in Chile, the Mayall z-band Legacy Survey (MzLS) in Arizona, and the Beijing-Arizona Sky Survey (BASS).

The Path to 3D Mapping

This 2D imaging survey records the positions and brightnesses of objects using visible and near-infrared light. While the current release provides a flat representation of the sky, it is designed to feed into the broader goals of DESI. By using spectra to determine the precise distances of the objects identified in this 2D atlas, scientists can convert the data into a three-dimensional cosmic map. DESI has already demonstrated significant momentum in this effort, having measured over 47 million galaxies and quasars, surpassing its initial target of 34 million.

Implications for Astronomy

The release of this atlas provides an unprecedented public resource for the global astronomical community. By making this volume of data available, the project enables researchers to more easily discover rare cosmic phenomena, such as black holes and gravitational lenses. Furthermore, the dataset acts as a foundational reference for upcoming high-profile observations from NASA's Nancy Grace Roman Space Telescope and the Vera C. Rubin Observatory.

Beyond individual discoveries, the map is a vital tool for studying the clustering of galaxies across cosmic time and investigating the nature of dark energy. The sheer scale of the data allows for a more granular analysis of how the universe has expanded and evolved.

Technical Execution and Next Steps

Bringing the atlas to fruition required significant computational power. Software development for the release spanned approximately one year, while the final image processing was completed in eight weeks using the Perlmutter supercomputer.

As the community begins to integrate this 2D data into their research, the focus remains on the transition to 3D. Astronomers will continue to use the atlas to refine target selection for DESI, ensuring that the resulting 3D map provides the most accurate possible picture of the universe's large-scale structure.