Dark Energy Spectroscopic Instrument

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Dark Energy Spectroscopic Instrument
DESI experiment design - 2016-02-12.jpg
DESI design concept in February, 2016
Alternative namesDESI Edit this at Wikidata
Part ofKitt Peak National Observatory
Nicholas U. Mayall Telescope Edit this on Wikidata
Location(s)Kitt Peak, Arizona, US
Coordinates31°57′30″N 111°35′48″W / 31.9583°N 111.5967°W / 31.9583; -111.5967Coordinates: 31°57′30″N 111°35′48″W / 31.9583°N 111.5967°W / 31.9583; -111.5967 Edit this at Wikidata
OrganizationLawrence Berkeley National Laboratory Edit this on Wikidata
Altitude2,100 m (6,900 ft) Edit this at Wikidata
Wavelength360 nm (830 THz)-980 nm (310 THz)
Built2015 Edit this on Wikidata (2015 Edit this on Wikidata) Edit this at Wikidata
First light2019 Edit this on Wikidata
Telescope stylescientific instrument
spectrometer Edit this on Wikidata
Websitedesi.lbl.gov Edit this at Wikidata
Dark Energy Spectroscopic Instrument is located in the United States
Dark Energy Spectroscopic Instrument
Location of Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) is a new instrument for conducting a spectrographic survey of distant galaxies. Its main components are a focal plane containing 5000 fiber-positioning robots, and a bank of spectrographs which are fed by the fibers. The new instrument will enable an experiment to probe the expansion history of the Universe and the mysterious physics of dark energy.[1][2]

The instrument is funded by the U.S. Department of Energy Office of Science and is now operating. It is located at 6880 ft., retrofitted onto the Mayall Telescope on top of Kitt Peak in the Sonoran Desert 55 miles distant from Tucson, Arizona. [3]

Science goals[edit]

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 diverse aspects of cosmology, from dark energy to alternatives to General Relativity to neutrino masses to the early 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.[4] 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.[5] 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.[6]

3D map of the Universe[edit]

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.[7] 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 beginning in September 2019, the DESI experiment will observe 35 million galaxies and quasars.[8]

Instrument design[edit]

The DESI instrument will implement a new highly multiplexed optical spectrograph on the Mayall Telescope.[9] A new optical corrector design creates a very large, 8.0 square degree field of view on the sky, which combined with the new focal plane instrumentation will weigh approximately 20,000 lbs. The focal plane accommodates 5,000 small computer controlled fiber positioners on a 10.4 millimeter pitch. The entire focal plane can be reconfigured for the next exposure in less than two minutes while the telescope slews to the next field.

The instrument fabrication is managed by the Lawrence Berkeley National Laboratory. Construction on the new instrument started in 2015.[10] Funding is provided by the Department of Energy Office of Science, the National Science Foundation, the Science and Technology Facilities Council of the U.K., by the Gordon and Betty Moore Foundation, by the Heising-Simons Foundation, and by collaborating institutions worldwide.


In October 2019, DESI achieved its first light test and was targeting full operations by 2020.[11]


  1. ^ Bebek, C.J., ed. (2015-06-15). "DESI Design Report". Retrieved 2016-02-12.
  2. ^ Pultarova, Tereza (February 16, 2018). "How 5,000 Pencil-Size Robots May Solve the Mysteries of the Universe". Live Science.
  3. ^ Telescope tracks 35 million galaxies in Dark Energy hunt, BBC Science report, 28 October 2019
  4. ^ Seo, Hee-Jong; Eisenstein, Daniel J. (2003). "Probing Dark Energy with Baryonic Acoustic Oscillations from Future Large Galaxy Redshift Surveys". The Astrophysical Journal. 598 (2): 720–740. arXiv:astro-ph/0307460. Bibcode:2003ApJ...598..720S. doi:10.1086/379122.
  5. ^ Albrecht, Andreas; et al. (2006). "Report of the Dark Energy Task Force". arXiv:astro-ph/0609591.
  6. ^ "Building for Discovery: Strategic Plan for U.S. Particle Physics in the Global Context" (PDF). May 2014.
  7. ^ Eisenstein, Daniel; et al. (2005). "Detection of the Baryon Acoustic Peak in the Large-Scale Correlation Function of SDSS Luminous Red Galaxies". The Astrophysical Journal. 633 (2): 560–574. arXiv:astro-ph/0501171. Bibcode:2005ApJ...633..560E. doi:10.1086/466512.
  8. ^ http://newscenter.lbl.gov/2016/08/09/3-d-galaxy-mapping-project-enters-construction-phase/
  9. ^ Levi, Michael; et al. (4 August 2013). "The DESI Experiment". arXiv:1308.0847 [astro-ph.CO].
  10. ^ Preuss, Paul (2015-09-21). "DESI, an Ambitious Probe of Dark Energy, Achieves its Next Major Milestone".
  11. ^ Lincoln, Don. "Super New Telescope Opens Its Eyes For The First Time". Forbes. Retrieved 2019-11-09.

External links[edit]