Dark Energy Spectroscopic Instrument Completes Five-Year Survey, Creates Largest 3D Map of the Universe

DESI Completes Five-Year Survey, Unveiling the Largest 3D Map of the Universe

The Dark Energy Spectroscopic Instrument (DESI) has completed its planned five-year survey, creating the largest and most detailed high-resolution 3D map of the universe to date. The survey, which began in May 2021 at Kitt Peak National Observatory in Arizona, finished ahead of schedule and collected data significantly exceeding its original targets.

The primary aim of the map is to study dark energy, the force thought to be responsible for the universe's accelerating expansion.

Analysis of preliminary data has suggested that dark energy may be evolving over time, a finding that will be tested further with the complete five-year dataset.

Survey Results and Data Collection

• Original Goal: The instrument was designed to gather data on 34 million galaxies and quasars.
• Actual Data Collected: DESI captured data on more than 47 million galaxies and quasars, and over 20 million nearby stars.
• Comparative Scale: The survey has measured cosmological data for approximately six times as many galaxies and quasars as all previous measurements combined.
• Milestone Observation: The final set of observations for the original mission saw the instrument's 5,000 fiber-optic components directed at a patch of sky near the Little Dipper.

Instrument and Operations

• Location: DESI is mounted on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory in Arizona.
• Technology: The instrument uses 5,000 robotic positioners to align optical fibers with high precision, feeding light into ten spectrographs.
• Data Transfer: Roughly 80 gigabytes of data are transferred nightly via the ESnet high-speed network to supercomputers at the National Energy Research Scientific Computing Center (NERSC) for processing.
• Efficiency: The survey was completed ahead of schedule, attributed to the instrument performing more efficiently than anticipated.

Project Management and Collaboration

• Management: The project is managed by the Department of Energy's Lawrence Berkeley National Laboratory.
• Researchers: The collaboration involves over 900 researchers from more than 70 institutions across 13-14 countries.
• Funding: DESI is supported by the DOE Office of Science, the National Energy Research Scientific Computing Center, the U.S. National Science Foundation, the Science and Technology Facilities Council of the United Kingdom, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, the French Alternative Energies and Atomic Energy Commission (CEA), the Secretariat of Science, Humanities, Technology and Innovation (SECIHTI) of Mexico, the Ministry of Science and Innovation of Spain, and DESI member institutions.

Scientific Objectives and Preliminary Findings

• Primary Goal: The 3D map is used to study dark energy, which is estimated to constitute about 70% of the universe and is associated with its accelerating expansion.
• Methodology: Researchers trace dark energy's influence over 11 billion years of cosmic history by comparing how galaxies were distributed in the past with their distribution today.
• Preliminary Finding: Analysis of data from the first three years of the survey has suggested that dark energy, previously assumed to be a constant force (as in the Lambda Cold Dark Matter model), might be evolving over time.
• Significance of Ongoing Analysis: The full five-year dataset will provide more data to test this preliminary finding. If confirmed, this would represent a significant departure from the standard cosmological model.

Operational Challenges

• COVID-19 Pandemic: Final tests of the instrument in 2020 were interrupted by the COVID-19 pandemic.
• Contreras Fire: In 2022, the Contreras Fire swept over Kitt Peak National Observatory. According to project reports, the fire did not damage the telescope. Recovery efforts were subsequently delayed by monsoons and mudslides.

Future Plans

• Data Processing: The collaboration will begin processing the completed five-year dataset.
• First Results: The first dark energy results from the full five-year survey are expected to be published in 2027.
• Extended Survey: DESI will continue observations through 2028 to extend the map's coverage from 14,000 to approximately 17,000 square degrees (an increase of about 20%).
• Extended Goals: The extended survey will focus on more challenging areas of the sky, collect data on more distant "luminous red galaxies," and study nearby dwarf galaxies and stellar streams to better understand dark matter.