A massive telescope in the Arizona desert has finished building the most detailed three-dimensional map of the universe ever assembled, and it did so ahead of schedule. The Dark Energy Spectroscopic Instrument, known as DESI, has now cataloged more than 47 million galaxies and quasars, each one pinpointed in space and time using its light signature. The result is a cosmic atlas stretching billions of years into the past, one that scientists say could reshape our understanding of dark energy, the mysterious force accelerating the expansion of the universe.
“DESI has given us an unprecedented view of the universe’s structure and history,” said Michael Levi, DESI project director at Lawrence Berkeley National Laboratory, in an April 2026 announcement marking the project’s milestone. The instrument, mounted on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, was originally designed for a five-year observing campaign. It wrapped up that work early, having captured spectra from its tens of millions of targets along with more than 20 million stars.
Why a 3D map matters
Previous surveys, most notably the Sloan Digital Sky Survey, mapped roughly four million objects over more than a decade of observations. DESI has surpassed that by an order of magnitude. But the real significance is not just the head count. Each object in the catalog comes with a spectrum, a breakdown of its light into component wavelengths that reveals how fast it is moving away from Earth. That speed, called redshift, tells scientists how far away the object is and when its light was emitted. Stitch millions of those measurements together and you get a three-dimensional picture of how matter is distributed across the cosmos, and how that distribution has changed over billions of years.
That picture is essential for studying dark energy. Since the late 1990s, physicists have known that the universe’s expansion is speeding up rather than slowing down, driven by something that makes up roughly 68 percent of the total energy in the cosmos. The simplest explanation, Albert Einstein’s cosmological constant, treats dark energy as a fixed property of space itself. But whether that model holds at every epoch of cosmic history is one of the biggest open questions in physics. DESI’s map provides the raw material to test it.
What the data shows so far
The collaboration has already released its first major dataset. Data Release 1, covering observations from May 2021 through June 2022, includes spectra and redshifts for more than 18 million unique targets. Processing that volume of data required the NERSC Perlmutter supercomputer and the ESnet high-speed research network, both operated by Lawrence Berkeley National Laboratory.
Several peer-reviewed studies built on DR1 have already produced significant results. One set of papers measured baryon acoustic oscillations, or BAO, a pattern imprinted on the distribution of matter by sound waves rippling through the hot plasma of the early universe. Those oscillations left a characteristic spacing between galaxies that acts as a “standard ruler,” letting scientists measure cosmic distances with high precision at different points in the universe’s history.
A separate analysis pushed those measurements to even greater distances using the Lyman-alpha forest, a series of absorption features in the light of distant quasars caused by intervening clouds of hydrogen gas. Together, the BAO and Lyman-alpha results span a wide range of cosmic epochs, from relatively recent times back to when the universe was only a few billion years old.
Notably, the DESI Year 1 BAO results, published in 2024, showed mild hints that dark energy might not behave as a simple cosmological constant. The data favored models in which dark energy’s strength changes over time, though the statistical significance was not strong enough to be conclusive. Whether those hints grow stronger with the full five-year dataset is one of the most closely watched questions in cosmology right now.
The collaboration has also released cosmology chains and supporting data products tied to its earlier DR1 BAO analyses, making its statistical fits publicly available so that independent researchers worldwide can reproduce the analysis and test alternative models. However, the Berkeley Lab announcement in April 2026 focused on the completion of the five-year observing campaign, not a full DR2 science release. A comprehensive second data release with its own accompanying science papers has not yet been published as of May 2026. That distinction matters: while the cosmology chains linked to DR1 results are accessible, the broader DR2 dataset covering the full survey remains in preparation.
What scientists are still working out
The full 47-million-object dataset has not yet been analyzed for its cosmological implications. The detailed papers interpreting the complete survey in the context of dark energy models have not appeared as of May 2026. Until those analyses are published and peer-reviewed, the strongest claims about dark energy’s behavior remain preliminary.
There are also technical challenges ahead. Combining measurements from different types of cosmic objects, such as galaxies, quasars, and the Lyman-alpha forest, can reveal systematic errors that single-tracer analyses miss. The technical paper describing DR1 documents the dataset’s calibration limits, but the full multi-tracer analysis across all five years of data will require additional validation that has not been completed.
DESI is also not working in isolation. The European Space Agency’s Euclid space telescope, launched in 2023, is conducting its own survey of the universe’s large-scale structure from orbit. The two projects use different methods and observe from different vantage points, which means their results can cross-check each other. Where they agree, confidence in the findings will be high. Where they diverge, the discrepancies could point to new physics or unresolved measurement issues.
What comes next for the survey
With its original five-year program complete, DESI is not shutting down. The instrument continues to observe, extending its reach to fainter and more distant objects. The collaboration, which involves more than 900 researchers from over 70 institutions across the globe, plans to release additional data products as processing continues.
For researchers or science enthusiasts who want to dig into the findings firsthand, the DR1 data products and associated cosmology chains are publicly accessible through the DESI data portal. Anyone with the technical background can download spectra, redshifts, and statistical fits and run independent analyses. That open-access approach turns a single collaboration’s observations into a shared scientific resource, one that will likely influence how physicists model the universe’s expansion for years to come.
Where DESI’s dark energy search stands in May 2026
The fundamental question DESI was built to answer, whether dark energy is truly constant or something more complex, remains open. But with 47 million data points now in hand, the tools to answer it have never been sharper.
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*This article was researched with the help of AI, with human editors creating the final content.
