MSGID: 1:317/3 6489427b   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    DESI early data release holds nearly two million objects    
      
     Date:   
         June 13, 2023   
     Source:   
         DOE/Lawrence Berkeley National Laboratory   
     Summary:   
         The first batch of data from the Dark Energy Spectroscopic   
         Instrument is now available for researchers to explore. Taken   
         during the experiment's 'survey validation' phase, the data include   
         distant galaxies and quasars as well as stars in our own Milky Way.   
      
      
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   FULL STORY   
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   The universe is big, and it's getting bigger. To study dark energy,   
   the mysterious force behind the accelerating expansion of our universe,   
   scientists are using the Dark Energy Spectroscopic Instrument (DESI)   
   to map more than 40 million galaxies, quasars, and stars. Today, the   
   collaboration publicly released its first batch of data, with nearly 2   
   million objects for researchers to explore.   
      
   The 80-terabyte data set comes from 2,480 exposures taken over six months   
   during the experiment's "survey validation" phase in 2020 and 2021. In   
   this period between turning the instrument on and beginning the official   
   science run, researchers made sure their plan for using the telescope   
   would meet their science goals -- for example, by checking how long it   
   took to observe galaxies of different brightness, and by validating the   
   selection of stars and galaxies to observe.   
      
   "The fact that DESI works so well, and that the amount of science-grade   
   data it took during survey validation is comparable to previous   
   completed sky surveys, is a monumental achievement," said Nathalie   
   Palanque-Delabrouille, co- spokesperson for DESI and a scientist at the   
   Department of Energy's Lawrence Berkeley National Laboratory (Berkeley   
   Lab), which manages the experiment.   
      
   "This milestone shows that DESI is a unique spectroscopic factory   
   whose data will not only allow the study of dark energy but will also   
   be coveted by the whole scientific community to address other topics,   
   such as dark matter, gravitational lensing, and galactic morphology."   
   Today the collaboration also published a set of papers related to the   
   early data release, which include early measurements of galaxy clustering,   
   studies of rare objects, and descriptions of the instrument and survey   
   operations. The new papers build on DESI's first measurement of the   
   cosmological distance scale that was published in April, which used the   
   first two months of routine survey data (not included in the early data   
   release) and also showed DESI's ability to accomplish its design goals.   
      
   DESI uses 5,000 robotic positioners to move optical fibers that capture   
   light from objects millions or billions of light-years away. It is the   
   most powerful multi-object survey spectrograph in the world, able to   
   measure light from more than 100,000 galaxies in one night. That light   
   tells researchers how far away an object is, building a 3D cosmic map.   
      
   "Survey validation was very important for DESI because it allowed us   
   -- before starting the main survey -- to adjust our selection of all   
   the objects, including stars, bright galaxies, luminous red galaxies,   
   emission line galaxies, and quasars," said Christophe Yeche, a scientist   
   with the French Alternative Energies and Atomic Energy Commission   
   (CEA) who co-leads the target selection group. "We've been able to   
   optimize our selection and confirm our observation strategy."  As the   
   universe expands, it stretches light's wavelength, making it redder --   
   a characteristic known as redshift. The further away the galaxy, the   
   bigger the redshift. DESI specializes in collecting redshifts that can   
   then be used to solve some of astrophysics' biggest puzzles: what dark   
   energy is and how it has changed throughout the universe's history.   
      
   While DESI's primary goal is understanding dark energy, much of the data   
   can also be used in other astronomical studies. For example, the early   
   data release contains detailed images from some well-known areas of the   
   sky, such as the Hubble Deep Field.   
      
   "There are some well-trodden spots where we've drilled down into the   
   sky," said Stephen Bailey, a scientist at Berkeley Lab who leads data   
   management for DESI.   
      
   "We've taken valuable spectroscopic images in areas that are of interest   
   to the rest of the community, and we're hoping that other people will take   
   this data and do additional science with it."  Two interesting finds have   
   already surfaced: Evidence of a mass migration of stars into the Andromeda   
   galaxy, and incredibly distant quasars, the extremely bright and active   
   supermassive black holes sometimes found at the center of galaxies.   
      
   "We observed some areas at very high depth. People have looked at that   
   data and discovered very high redshift quasars, which are still so rare   
   that basically any discovery of them is useful," said Anthony Kremin,   
   a postdoctoral researcher at Berkeley Lab who led the data processing   
   for the early data release. "Those high-redshift quasars are usually   
   found with very large telescopes, so the fact that DESI -- a smaller,   
   4-meter survey instrument - - could compete with those larger, dedicated   
   observatories was an achievement we are pretty proud of and demonstrates   
   the exceptional throughput of the instrument."  Survey validation was   
   also a chance to test the process of transforming raw data from DESI's   
   ten spectrometers (which split a galaxy's light into different colors)   
   into useful information.   
      
   "If you looked at them, the images coming directly from the camera would   
   look like nonsense -- like lines on a weird, fuzzy image," said Laurie   
   Stephey, a data architect at the National Energy Research Scientific   
   Computing Center (NERSC), the supercomputer that processes DESI's   
   data. "The magic happens in the processing and the software being able   
   to decode the data. It's exciting that we have the technology to make   
   that data accessible to the research community and that we can support   
   this big question of 'what is dark energy?'"  DESI's early data was a   
   unique project for NERSC. All of the experiment's code, including the   
   computational heavy lifting, is written in the programming language   
   Python rather than the traditional C++ or Fortran.   
      
   "That was the first time that using pure Python was shown to be a   
   feasible approach for a major experiment at NERSC, and since then,   
   Python has become increasingly common in our user workload," Stephey said.   
      
   The DESI early data release is now available to access for free through   
   NERSC.   
      
   There is plenty of data yet to come from the experiment. DESI is   
   currently two years into its five-year run and ahead of schedule on its   
   quest to collect more than 40 million redshifts. The survey has already   
   catalogued more than 26 million astronomical objects in its science run,   
   and is adding more than a million per month.   
      
   DESI is supported by the DOE Office of Science and by the National   
   Energy Research Scientific Computing Center, a DOE Office of Science   
   user facility.   
      
   Additional support for DESI is provided by the U.S. National Science   
   Foundation, the Science and Technologies 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 National Council of Science and Technology of Mexico, the   
   Ministry of Economy of Spain, and by the DESI member institutions.   
      
   Kitt Peak National Observatory is a program of NSF's NOIRLab.   
      
   The DESI collaboration is honored to be permitted to conduct scientific   
   research on Iolkam Du'ag (Kitt Peak), a mountain with particular   
   significance to the Tohono O'odham Nation.   
      
   Further information: https://data.desi.lbl.gov/doc/papers/   
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Astrophysics # Galaxies # Dark_Matter # Astronomy #   
                   Black_Holes # Cosmology # Space_Telescopes # Big_Bang   
       * RELATED_TERMS   
             o Quasar o Galaxy o Hubble_Deep_Field o Dark_matter o   
             Magellanic_Clouds o Globular_cluster o Milky_Way o Edwin_Hubble   
      
   ==========================================================================   
   Story Source: Materials provided by   
   DOE/Lawrence_Berkeley_National_Laboratory. Original written by Lauren   
   Biron. Note: Content may be edited for style and length.   
      
      
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230613110102.htm   
      
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