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These results have had a very significant impact on the scientific community, and DESI continues its observations until the end of 2028 to confirm this potential major discovery.
This figure represents a thin slice of the map of the Universe produced by DESI over five years. It shows galaxies and quasars. Earth is at the center of the sections, and the black area marks where our own galaxy obscures distant objects. Light from the most distant galaxies shown took 11 billion years to reach Earth.
Credit: Claire Lamman/DESI Collaboration
During the night of April 14 to 15, 2026, the DESI collaboration observed the final "tile" of the originally planned survey (a tile corresponds to a telescope pointing at a region of the sky covering about 8 square degrees, or 16 times the area of the full moon). For 5 years, every 20 minutes, the DESI instrument switched tiles and measured the spectra of 5000 new galaxies, covering more than a third of the sky.
DESI's goal was to capture the light of 34 million galaxies and quasars (extremely distant but bright objects with black holes at their centers) over five years. DESI actually observed more than 47 million galaxies and quasars, plus 20 million stars.
Building on this instrumental success, the DESI survey will continue for another two and a half years until the end of 2028.
This time-lapse video shows how the DESI spectroscopic instrument built its observation map over five years. Each "tile" represents a telescope pointing where DESI records the spectra of thousands of objects simultaneously. The tiles overlap to densify the map, with most areas observed multiple times. The observations shown here were collected during the "Dark-Time Survey," a campaign targeting the faintest and most distant objects DESI can observe, located billions of light-years away.
DESI data: Anand Raichoor/DESI collaboration
Sky map: Axel Mellinger, A Color All-Sky Panorama Image of the Milky Way, Publ. Astron. Soc. Pacific 121, 1180-1187 (2009)
DESI data: Anand Raichoor/DESI collaboration
Sky map: Axel Mellinger, A Color All-Sky Panorama Image of the Milky Way, Publ. Astron. Soc. Pacific 121, 1180-1187 (2009)
The spectrum of each galaxy and quasar measured by DESI is analyzed to determine their positions in the largest and densest three-dimensional map of the Universe to date. Researchers use this map to explore dark energy, a fundamental ingredient that makes up about 70% of our Universe and drives its accelerated expansion.
By observing the distribution of galaxies in the Universe, researchers have traced the influence of dark energy over 11 billion years of cosmic history, which began about 13.8 billion years ago. Surprising results obtained from the first three years of DESI observations suggest that dark energy, long considered a cosmological constant, might actually evolve over time. These results, whose scientific papers are the most cited in 2025, have had a very strong impact even beyond the cosmological community.
With the full set of five years of data, researchers will have much more information to verify whether this hypothesis holds. If confirmed, it would mark a major shift in our understanding of the Universe and its fate, which depends on the balance between matter and dark energy. Should we modify the theory of general relativity, or is it necessary to invoke a fifth force?
DESI has now measured cosmological data for six times more galaxies and quasars than all previous surveys combined. The collaboration has already begun processing the full dataset, with the next results on dark energy from the complete five-year DESI mapping expected in 2027.
What's next?
Teams are working to define a scientific program and technical improvements to continue the incredible harvest of science already underway. The scientific program for the "DESI-2" phase would be based on four pillars.
First, a survey with ten times higher density than DESI for the last 8 billion years of cosmic evolution (redshift less than 1) to study the nature of dark energy and test the theory of general relativity.
Second, a survey targeting the Universe when it was 2 to 4 billion years old, an era when the Universe still faithfully reflects the primordial initial conditions, which is very sensitive to the cosmic inflation model and the sum of neutrino masses.
The third component of the survey aims to measure the spectra of tens of millions of stars in the Milky Way and the "Local Group," including the first extensive survey of the Andromeda galaxy, with the goal of better understanding local dynamics and dark matter.
Finally, a strong synergy with the Rubin-LSST observatory is planned. The DESI-2 program would begin in 2029 for a duration of 6 years and will make way for future large surveys for which instruments are being studied, such as the Widefield Spectroscopic Telescope with a first light expected in 2040.