DESI releases biggest 2D map of the universe

The DESI Legacy Imaging Surveys team has unveiled the largest-ever 2D color map of the universe, capturing nearly 4 billion celestial objects across a vast expanse of the night sky. The map, composed of 5.6 trillion pixels, offers an unprecedented level of detail, allowing researchers and amateur astronomers alike to study the cosmos in ways previously unimaginable. The release marks a major milestone in observational astronomy, providing a foundational resource for understanding the structure, evolution, and mysteries of the universe. The map covers approximately 75% of the sky, spanning visible and near-infrared wavelengths, and includes regions not obscured by the dense dust and stars of the Milky Way. This deep view of the extragalactic universe allows scientists to examine distant galaxies, identify rare cosmic phenomena such as gravitational lenses, and track transient events like supernovae. The data is freely accessible to the public via the Legacy Survey Sky Viewer, enabling both professional researchers and citizen scientists to engage with the findings directly. The creation of the map relied on contributions from over 160 scientists who collected data using multiple ground-based sky surveys. These included the Dark Energy Camera Legacy Survey (DECaLS) at the NSF Cerro Tololo Inter-American Observatory, the Mayall z-band Legacy Survey (MzLS) at the NSF Kitt Peak National Observatory, and the Beijing-Arizona Sky Survey (BASS) at the University of Arizona’s Steward Observatory. Additional data came from NASA’s Wide-field Infrared Survey Explorer (WISE) satellite and other public datasets. The final dataset was compiled by a dedicated team of 20 individuals, ensuring accuracy and completeness. Among the notable features of the map is the inclusion of well-known celestial objects such as the spiral galaxy Messier 96, located approximately 35 million light-years away. Captured using the 570-megapixel Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter Telescope at CTIO in Chile, this image highlights the precision and scale of the survey. Similarly, the Copeland Septet, a group of galaxies in the constellation Leo, was also documented, showcasing the diversity of galactic structures within the mapped region. The DESI Legacy Imaging Surveys were initially designed to support the upcoming Dark Energy Spectroscopic Instrument (DESI) survey, which aims to map the distribution of galaxies in three dimensions. The 2D map serves as a critical preparatory step, offering a detailed reference for identifying and analyzing objects before spectroscopic measurements are taken. By recording the positions and brightness of galaxies and stars, the map helps establish a baseline for future studies on cosmic expansion and galaxy formation. David Schlegel, a co-lead of the Legacy Surveys and a scientist at the Department of Energy’s Lawrence Berkeley National Laboratory, emphasized the significance of the work. “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,” he explained. The map has become an essential tool for modern astronomy, with over 1,800 scientific papers referencing the data so far. Its impact extends beyond academic research, inspiring public engagement and fostering a deeper appreciation for the cosmos. Arjun Dey, another co-lead of the project and an astronomer at NSF NOIRLab, added that the data represents a shared human achievement. “For our team, these data are fundamental to our investigation of the expansion history of the universe and the formation of our galaxy,” he noted. “But the skies belong to everyone, and this survey gives everyone the chance to explore the sky and marvel at its wonders.” The open-access nature of the map ensures that its benefits extend to educators, students, and enthusiasts worldwide.