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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Dark Energy Spectroscopic Instrument | 1/3 | https://en.wikipedia.org/wiki/Dark_Energy_Spectroscopic_Instrument | reference | science, encyclopedia | 2026-05-05T11:05:15.924157+00:00 | kb-cron |
The Dark Energy Spectroscopic Instrument (DESI) is a scientific research instrument for conducting spectrographic astronomical surveys of distant galaxies. Its main components are a focal plane containing 5,000 fiber-positioning robots, and a bank of spectrographs which are fed by the fibers. The instrument enables an experiment to probe the expansion history of the universe and the mysterious physics of dark energy. The main DESI survey started in May 2021. DESI sits at an elevation of 6,880 feet (2,100 m), where it has been retrofitted onto the Mayall Telescope on top of Kitt Peak in the Sonoran Desert, which is located 55 miles (89 km) from Tucson, Arizona, United States. The instrument is operated by the Lawrence Berkeley National Laboratory under funding from the U.S. Department of Energy's Office of Science. Construction of the instrument was principally funded by the U.S. Department of Energy's Office of Science, and by other numerous sources including the U.S. National Science Foundation, the British Science and Technology Facilities Council, France's Alternative Energies and Atomic Energy Commission, Mexico's National Council of Science and Technology, Spain's Ministry of Science and Innovation, by the Gordon and Betty Moore Foundation, by the Heising-Simons Foundation, and by collaborating institutions worldwide.
== Scientific goals ==
The expansion history and large-scale structure of the universe is a key prediction of cosmological models, and DESI observations will permit scientists to probe various aspects of cosmology, including dark energy, alternatives to general relativity, neutrino masses, and the primordial universe. The data from DESI will be used to create three-dimensional maps of the distribution of matter covering an unprecedented volume of the universe with unparalleled detail. This will provide insight into the nature of dark energy and establish whether cosmic acceleration is due to a cosmic-scale modification of General Relativity. DESI will be transformative in the understanding of dark energy and the expansion rate of the universe at early times, one of the greatest mysteries in the understanding of the physical laws. DESI will measure the expansion history of the universe using the baryon acoustic oscillations (BAO) imprinted in the clustering of galaxies, quasars, and the intergalactic medium. The BAO technique is a robust way to extract cosmological distance information from the clustering of matter and galaxies. It relies only on very large-scale structure and it does so in a manner that enables scientists to separate the acoustic peak of the BAO signature from uncertainties in most systematic errors in the data. BAO was identified in the 2006 Dark Energy Task Force report as one of the key methods for studying dark energy. In May 2014, the High-Energy Physics Advisory Panel, a federal advisory committee, commissioned by the US Department of Energy (DOE) and the National Science Foundation (NSF) endorsed DESI.
== 3D map of the universe ==
The baryon acoustic oscillations method requires a three-dimensional map of distant galaxies and quasars created from the angular and redshift information of a large statistical sample of cosmologically distant objects. By obtaining spectra of distant galaxies it is possible to determine their distance, via the measurement of their spectroscopic redshift, and thus create a 3-D map of the universe. The 3-D map of the large-scale structure of the universe also contains more information about dark energy than just the BAO and is sensitive to the mass of the neutrino and parameters that governed the primordial universe. During its five-year survey, which began on May 15, 2021, the DESI experiment is expected to observe 40 million galaxies and quasars.