Collaboration, founded 2021
Dark Energy Spectroscopic Instrument (DESI)
DESI is a 5,000-fiber spectrograph on the Mayall Telescope in Arizona that maps the universe in 3D. Its data hint that dark energy may be weakening.
- Location
- Nicholas U. Mayall 4-meter Telescope, Kitt Peak National Observatory, Arizona
- Focus
- Dark energy, Cosmology, Galaxies, Future of the universe
- Coordinates
- 31.964, -111.600
The Dark Energy Spectroscopic Instrument (DESI) is a survey instrument on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, Arizona. It measures the distances to millions of galaxies and quasars to build a 3D map of the universe and track how dark energy has shaped cosmic expansion over 11 billion years. Lawrence Berkeley National Laboratory operates it for the US Department of Energy, with more than 900 researchers from over 70 institutions.
Flagship instruments
- 5,000 robotic fiber positioners: each fiber is placed on a target, so DESI takes 5,000 spectra at once and moves to a new patch of sky roughly every 20 minutes.
Recent results
DESI uses baryon acoustic oscillations, a “standard ruler” first detected in galaxy maps in 2005. Its first-year results gave the first hint in decades that dark energy might not be constant. The 2025 DR2 analysis, with more than 14 million galaxies and quasars, preferred an evolving dark energy at 3.1 sigma with CMB data, and 2.8 to 4.2 sigma with supernovae added. In July 2026 a Lyman-alpha analysis moved slightly back toward the standard model (2.7 and 3.2 sigma), still short of the 5-sigma discovery threshold. On April 14, 2026, DESI completed its planned five-year map ahead of schedule, with more than 47 million galaxies and quasars against a goal of 34 million, plus more than 20 million stars.
What to watch, 2026-2030
- 2027: first dark energy results from the full five-year dataset.
- Through 2028: extended observations to enlarge the map.
Why scientists are converging here
If dark energy changes over time, forecasts for the future of the universe change with it. In our Research Pulse count, “DESI” appeared in 468 astro-ph abstracts from April to September 2026, up 12.5% on the previous six months, while the generic phrase “dark energy” slipped 4%. Abstract mentions are a proxy for attention, not evidence, but they suggest the field is focusing on DESI’s data specifically. Euclid and the Rubin Observatory will provide the independent checks.