Free Astronomy Magazine July-August 2026

43 JULY-AUGUST 2026 ASTRO PUBLISHING T he 5,000 fiber-optic eyes of the Dark Energy Spectroscopic Instrument (DESI) swiveled onto a patch of sky near the Little Dipper. Roughly every 20 minutes, they locked onto distant pinpricks of light, gathering photons that had traveled toward Earth for bil- lions of years. When the Sun rose, DESI collaborators marked the com- pletion of a major milestone: suc- cessfully surveying all of the area in DESI’s planned map of the Universe. The five-year survey, finished ahead of schedule and with vastly more data than expected, has produced the largest high-resolution 3D map of the Universe ever made. Re- searchers use that map to explore dark energy, the fundamental in- gredient that makes up about 70% of our Universe and is driving its ac- celerating expansion. DESI’s quest to understand dark en- ergy is a global endeavor. The inter- national experiment brings to- gether the expertise of more than 900 researchers (including 300 PhD students) from over 70 institutions. The project is managed by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), and the instrument was constructed and is operated with funding from the DOE Office of Science. DESI is mounted on the U.S. National Science Foundation Nicholas U. Mayall 4-meter Tele- scope at NSF Kitt Peak National Ob- servatory (KPNO) in Arizona, a Program of NSF NOIRLab. By comparing how galaxies clus- tered in the past with their distribu- tion today, researchers can trace dark energy’s influence over 11 bil- lion years of cosmic history. Surpris- ing results using DESI’s first three years of data hinted that dark en- ergy, once thought to be a “cosmo- logical constant,” might be evolving over time. With the full set of five years of data, researchers will have significantly more information to test whether that hint disappears or grows. If confirmed, it would mark a major shift in how we think about our Universe and its potential fate, which hinges on the balance be- tween matter and dark energy. “It’s impossible to capture every- thing that went into making DESI such a successful experiment. From instrument builders and software engineers to technicians, observa- tory staff, and scientists — including many early-career researchers — it truly took a village,” says Stephanie Juneau, associate astronomer and NSF NOIRLab representative for DESI. “Ultimately, we are doing this for all humanity, to better under- stand our Universe and its eventual fate. After finding hints that dark energy might deviate from a con- stant, potentially altering that fate, this moment feels like sitting on the edge of my seat as we analyze the new map to see whether those hints will be confirmed. I’m also very intrigued by the many other discoveries that await in this new dataset.” “The Dark Energy Spectroscopic In- strument has truly exceeded all ex- pectations, delivering an unprece- dented 3D map of the Universe that will revolutionize our understand- ing of dark energy,” says Kathy Turner, Program Manager for the Cosmic Frontier in the Office of High Energy Physics at the Depart- ment of Energy. “From its incep- tion, we envisioned a project that would push the boundaries of cos- mology, and to see it come to such a spectacularly successful comple- tion for its initial survey, ahead of schedule and with such rich data, is incredibly rewarding. The dedica- tion and ingenuity of the entire DESI collaboration have made this world-leading science a reality, and I am immensely proud of the groundbreaking results we are al- T he band of the Milky Way stretches across the sky above U.S. National Science Foundation Kitt Peak National Observatory (KPNO), a Program of NSF NOIR- Lab. The largest telescope in this image is the NSF Nicholas U. Mayall 4-meter Telescope, which houses the Dark Energy Spectro- scopic Instrument (DESI). City lights from Tucson, Arizona are visible in the distance. [KPNO/ NOIRLab/NSF/AURA/P. Horálek (Institute of Physics in Opava)]