The Dark Energy Spectroscopic Instrument (DESI) has finished its five‑year survey, delivering the highest‑resolution three‑dimensional map of the cosmos ever produced. Over 47 million galaxies and quasars spanning 11 billion years of history were catalogued, exceeding the data volume originally planned. Researchers say the map’s unprecedented detail will let them test whether dark energy is truly constant. The achievement showcases large‑scale spectroscopic surveys for precision cosmology.

DESI captures light from up to 5,000 objects simultaneously, using robotic fiber positioners and ten spectrographs to split the light into its constituent colors. Each night generates roughly 80 GB of spectra that stream to Berkeley Lab’s supercomputers for analysis. Early results hinted at a weakening dark energy signal at 3.5–4.2 sigma, tantalizing but short of discovery. These measurements will refine the Hubble constant and test quintessence.

Completing the survey on schedule required navigating a pandemic, a wildfire that blacked out Kitt Peak, and a cyber‑attack on NOIRLab facilities. The team’s backup “Sneakernet” drives and a Starlink link kept data flowing when conventional networks failed. With the map in hand, cosmologists can now measure baryon acoustic oscillations across cosmic time and finally settle the dark‑energy debate. The dataset will serve as a legacy.