The DESI (Dark Energy Spectroscopic Instrument) collaboration has published the largest astrophysical catalog, a 3D map of the universe featuring 18.7 million objects including stars, galaxies, and quasars.
While the experiment’s primary mission is to shed light on dark energy, DESI’s Data Release 1 (DR1) could yield discoveries in other areas of astrophysics, such as the evolution of galaxies and black holes, the nature of dark matter, and the structure of the Milky Way.
DESI is an international experiment bringing together more than 900 researchers from over 70 institutions. The project is led by Berkeley Lab. DESI is installed on the 4-meter Nicholas U. Mayall Telescope at Kitt Peak Observatory, Arizona.
The new dataset greatly expands DESI’s Early Data Release (EDR), which contains approximately ten times more data and covers seven times the area of the sky. DR1 includes information from the first year of the main survey, collected between May 2021 and June 2022, as well as from the previous five months of survey validation, where researchers tested the experiment.
Objects in DESI’s catalog range from nearby stars in our Milky Way to galaxies billions of light-years away. Because of the time it takes for light to travel to Earth, observing space is like looking back in time. DESI allows us to see our universe at different times, from the present day to 11 billion years ago.
Although DR1 is only a fraction of what DESI will eventually produce, the 270-terabyte dataset represents a staggering amount of information, including precise distances to millions of galaxies, according to a Berkeley Lab release. The release contains more than twice as many extragalactic objects (those outside our galaxy) as collected in all previous 3D surveys combined.
3D MAP OF THE UNIVERSE
In 2024, DESI researchers used DR1 data to create the largest 3D map of our universe to date and make world-leading dark energy measurements.
“The DESI project has maintained the pace of creating 3D maps of the universe ten times larger every decade,” said David Schlegel, one of the DESI principal scientists at Berkeley Lab. “That’s our version of Moore’s Law for cosmological studies. The rapid progress is due to the clever combination of better instrument designs, technologies, and analysis of increasingly faint galaxies.”
HOW IT WORKS
DESI captures light from distant galaxies using 5,000 fiber-optic “eyes.” Under clear observing conditions, the instrument can image a new set of 5,000 objects approximately every 20 minutes, or more than 100,000 galaxies in one night. “DESI is unique in its ability to observe independent objects simultaneously,” said John Moustakas, professor of physics at Siena College and co-director of DR1.
The instrument separates the light from each galaxy into its color spectrum. This allows researchers to determine how much the light has been “redshifted,” or stretched toward the red end of the spectrum due to the expansion of the universe. Measuring the redshift of a distant object’s light tells scientists its distance, which means DESI can map the cosmos in three dimensions and reconstruct a detailed history of cosmic growth.
