DESI completes five-year survey at Mayall Telescope, Arizona; largest high-res 3D map 47M galaxies and quasars.

EPFL helps complete the largest 3D map of the universe ever made - EPFL

EPFL helps complete the largest 3D map of the universe ever made

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The Dark Energy Spectroscopic Instrument has completed its five-year mission to map more than 47-million galaxies and quasars.

Researchers, including from EPFL’sLaboratory of Astrophysics(LASTRO), expected to gather data on 34-million galaxies and quasars during the five-year survey, but the instrument performed so efficiently that it captured more than 47-million galaxies and quasars, plus more than 20 million nearby stars used to study the Milky Way.

A five-year survey - completed early

The five-year survey finished ahead of schedule, with vastly more data than expected and has produced the largest high-resolution 3D map of the universe ever made. Researchers use that map to explore dark energy, the fundamental ingredient that makes up about 70% of our universe and is driving its accelerating expansion.

By comparing how galaxies clustered in the past with their distribution today, they have traced dark energy’s influence over 11 billion years of cosmic history.

Surprising results using DESI’s first three years of data hinted that dark energy, once thought to be a “cosmological 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 between matter and dark energy.

“I have been involved from the very beginning of the survey, analyzing the first data collected by DESI during my PhD, and it has been incredible to witness this change in scale compared to previous experiments. DESI is a great example of how new technologies can drive scientific progress. Its scientific results have already challenged the standard cosmological model and Einstein’s cosmological constant and the full DESI dataset will be crucial in turning this trend into solid scientific evidence—and perhaps in revealing even more surprises,” explained Antoine Rocher, a cosmologist in the Laboratory of Astrophysics at EPFL.

DESI’s quest to understand dark energy is a global endeavor. The international experiment brings together the expertise of more than 900 researchers 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 is mounted on the U.S. National Science Foundation’s Nicholas U. Mayall 4-meter Telescope atKitt Peak National Observatory(a program of NSF NOIRLab) in Arizona.

DESI has now measured cosmological data for six times as many galaxies and quasars as all previous measurements combined. The collaboration will immediately begin processing the completed dataset, with the first dark energy results from DESI’s full five-year survey expected in 2027.

In the meantime, DESI scientists continue to analyze the survey’s first three years of data, refining dark energy measurements and producing additional results on the structure and evolution of the universe.

DESI will continue observations through 2028 and grow its map by about 20%, from 14,000 square degrees to 17,000 square degrees, covering parts of the sky that are more challenging to observe: areas that are closer to the plane of the Milky Way, where bright nearby stars can make it harder to see more distant objects, or further to the south, where the telescope must account for peering through more of Earth’s atmosphere.

The experiment will also revisit the existing area of the map to collect data from a new set of galaxies: more distant and faint “luminous red galaxies.” These will provide an even denser and more detailed map in the regions DESI has already covered, giving researchers a clearer picture of the Universe’s history.

“Being part of DESI continues to be a privilege — this is the kind of dataset that redefines what cosmology can do. Thanks to the instrument’s remarkable efficiency in cataloguing galaxies at roughly four times the speed of its predecessor, we completed the planned survey ahead of schedule with far richer data than we had dared to hope for. With the collaboration now committed to an eight-year program, arguably the best science is still to come — including the more decisively testing of whether dark energy is truly a constant or something far more exotic,” concluded Rafaela Gsponer, a scientist with LASTRO.

The DESI collaboration is honored to be permitted to conduct scientific research on I’oligam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.

credit for the image: Star trails over the Mayall Telescope that houses DESI. Credit: Luke Tyas

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The Dark Energy Spectroscopic Instrument (DESI), one of the most extensive surveys of the cosmos ever conducted, has finished all observations for its originally planned 3D map of the universe ahead of schedule.Researchers, including from EPFL’sLaboratory of Astrophysics(LASTRO), expected to gather data on 34-million galaxies and quasars during the five-year survey, but the instrument performed so efficiently that it captured more than 47-million galaxies and quasars, plus more than 20 million nearby stars used to study the Milky Way.A five-year survey - completed earlyThe five-year survey finished ahead of schedule, with vastly more data than expected and has produced the largest high-resolution 3D map of the universe ever made. Researchers use that map to explore dark energy, the fundamental ingredient that makes up about 70% of our universe and is driving its accelerating expansion.By comparing how galaxies clustered in the past with their distribution today, they have traced dark energy’s influence over 11 billion years of cosmic history.Surprising results using DESI’s first three years of data hinted that dark energy, once thought to be a “cosmological 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 between matter and dark energy.“I have been involved from the very beginning of the survey, analyzing the first data collected by DESI during my PhD, and it has been incredible to witness this change in scale compared to previous experiments. DESI is a great example of how new technologies can drive scientific progress. Its scientific results have already challenged the standard cosmological model and Einstein’s cosmological constant and the full DESI dataset will be crucial in turning this trend into solid scientific evidence—and perhaps in revealing even more surprises,” explained Antoine Rocher, a cosmologist in the Laboratory of Astrophysics at EPFL.An observing machineDESI’s quest to understand dark energy is a global endeavor. The international experiment brings together the expertise of more than 900 researchers 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 is mounted on the U.S. National Science Foundation’s Nicholas U. Mayall 4-meter Telescope atKitt Peak National Observatory(a program of NSF NOIRLab) in Arizona.DESI has now measured cosmological data for six times as many galaxies and quasars as all previous measurements combined. The collaboration will immediately begin processing the completed dataset, with the first dark energy results from DESI’s full five-year survey expected in 2027.In the meantime, DESI scientists continue to analyze the survey’s first three years of data, refining dark energy measurements and producing additional results on the structure and evolution of the universe.The sky’s the limitDESI will continue observations through 2028 and grow its map by about 20%, from 14,000 square degrees to 17,000 square degrees, covering parts of the sky that are more challenging to observe: areas that are closer to the plane of the Milky Way, where bright nearby stars can make it harder to see more distant objects, or further to the south, where the telescope must account for peering through more of Earth’s atmosphere.The experiment will also revisit the existing area of the map to collect data from a new set of galaxies: more distant and faint “luminous red galaxies.” These will provide an even denser and more detailed map in the regions DESI has already covered, giving researchers a clearer picture of the Universe’s history.“Being part of DESI continues to be a privilege — this is the kind of dataset that redefines what cosmology can do. Thanks to the instrument’s remarkable efficiency in cataloguing galaxies at roughly four times the speed of its predecessor, we completed the planned survey ahead of schedule with far richer data than we had dared to hope for. With the collaboration now committed to an eight-year program, arguably the best science is still to come — including the more decisively testing of whether dark energy is truly a constant or something far more exotic,” concluded Rafaela Gsponer, a scientist with LASTRO.The DESI collaboration is honored to be permitted to conduct scientific research on I’oligam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.