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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Astrophysicists confirm the faintest galaxy ever seen in the early   
   universe    
    The small, distant galaxy JD1 is typical of the kind that burned through   
   hydrogen left over from the Big Bang    
      
     Date:   
         June 1, 2023   
     Source:   
         University of California - Los Angeles   
     Summary:   
         After the Big Bang, the universe expanded and cooled sufficiently   
         for hydrogen atoms to form. In the absence of light from the first   
         stars and galaxies, the universe entered a period known as the   
         cosmic dark ages.   
      
         The first stars and galaxies appeared several hundred million   
         years later and began burning away the hydrogen fog left over   
         from the Big Bang, rendering the universe transparent, like it is   
         today. Researchers have now confirmed the existence of a distant,   
         faint galaxy typical of those whose light burned through the   
         hydrogen atoms; the finding should help them understand how the   
         cosmic dark ages ended.   
      
      
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   FULL STORY   
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   After the Big Bang, the universe expanded and cooled sufficiently for   
   hydrogen atoms to form. In the absence of light from the first stars   
   and galaxies, the universe entered a period known as the cosmic dark ages.   
      
   The first stars and galaxies appeared several hundred million years later   
   and began burning away the hydrogen fog left over from the Big Bang,   
   rendering the universe transparent, like it is today.   
      
   Researchers led by astrophysicists from UCLA confirmed the existence of   
   a distant, faint galaxy typical of those whose light burned through the   
   hydrogen atoms; the finding should help them understand how the cosmic   
   dark ages ended.   
      
   An international research team led by UCLA astrophysicists has confirmed   
   the existence of the faintest galaxy ever seen in the early universe. The   
   galaxy, called JD1, is one of the most distant identified to date, and   
   it is typical of the kinds of galaxies that burned through the fog of   
   hydrogen atoms left over from the Big Bang, letting light shine through   
   the universe and shaping it into what exists today.   
      
   The discovery was made using NASA's James Webb Space Telescope, and the   
   findings are published in the journal Nature.   
      
   The first billion years of the universe's life were a crucial period   
   in its evolution. After the Big Bang, approximately 13.8 billion years   
   ago, the universe expanded and cooled sufficiently for hydrogen atoms   
   to form. Hydrogen atoms absorb ultraviolet photons from young stars;   
   however, until the birth of the first stars and galaxies, the universe   
   became dark and entered a period known as the cosmic dark ages. The   
   appearance of the first stars and galaxies a few hundred million years   
   later bathed the universe in energetic ultraviolet light which began   
   burning, or ionizing, the hydrogen fog. That, in turn, enabled photons   
   to travel through space, rendering the universe transparent.   
      
   Determining the types of galaxies that dominated that era -- dubbed the   
   Epoch of Reionization -- is a major goal in astronomy today, but until   
   the development of the Webb telescope, scientists lacked the sensitive   
   infrared instruments required to study the first generation of galaxies.   
      
   "Most of the galaxies found with JWST so far are bright galaxies that   
   are rare and not thought to be particularly representative of the young   
   galaxies that populated the early universe," said Guido Roberts-Borsani,   
   a UCLA postdoctoral researcher and the study's first author. "As such,   
   while important, they are not thought to be the main agents that burned   
   through all of that hydrogen fog.   
      
   "Ultra-faint galaxies such as JD1, on the other hand, are far more   
   numerous, which is why we believe they are more representative of the   
   galaxies that conducted the reionization process, allowing ultraviolet   
   light to travel unimpeded through space and time."  JD1 is so dim and so   
   far away that it is challenging to study without a powerful telescope --   
   and a helping hand from nature. JD1 is located behind a large cluster   
   of nearby galaxies, called Abell 2744, whose combined gravitational   
   strength bends and amplifies the light from JD1, making it appear larger   
   and 13 times brighter than it otherwise would. The effect, known as   
   gravitational lensing, is similar to how a magnifying glass distorts and   
   amplifies light within its field of view; without gravitational lensing,   
   JD1 would likely have been missed.   
      
   The researchers used the Webb Telescope's near-infrared spectrograph   
   instrument, NIRSpec, to obtain an infrared light spectrum of the galaxy,   
   allowing them to determine its precise age and its distance from Earth,   
   as well as the number of stars and amount of dust and heavy elements   
   that it formed in its relatively short lifetime.   
      
   The combination of the galaxy's gravitational magnification and new images   
   from another one of the Webb Telescope's near-infrared instruments,   
   NIRCam, also made it possible for the team to study the galaxy's   
   structure in unprecedented detail and resolution, revealing three main   
   elongated clumps of dust and gas that are forming stars. The team used   
   the new data to trace JD1's light back to its original source and shape,   
   revealing a compact galaxy just a fraction of the size of older galaxies   
   like the Milky Way, which is 13.6 billion years old.   
      
   Because light takes time to travel to Earth, JD1 is seen as it was   
   approximately 13.3 billion years ago, when the universe was only about 4%   
   of its present age.   
      
   "Before the Webb telescope switched on, just a year ago, we could not   
   even dream of confirming such a faint galaxy," said Tommaso Treu, a UCLA   
   physics and astronomy professor, and the study's second author. "The   
   combination of JWST and the magnifying power of gravitational lensing   
   is a revolution. We are rewriting the book on how galaxies formed and   
   evolved in the immediate aftermath of the Big Bang."   
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Astrophysics # Galaxies # Big_Bang # Cosmology #   
                   Astronomy # NASA # Space_Telescopes # Stars   
       * RELATED_TERMS   
             o Galaxy_formation_and_evolution o Big_Bang_nucleosynthesis o   
             Big_Bang o Cosmic_microwave_background_radiation o Dark_matter   
             o Atom o Galaxy o Large-scale_structure_of_the_cosmos   
      
   ==========================================================================   
   Story Source: Materials provided by   
   University_of_California_-_Los_Angeles. Original written by Holly   
   Ober. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Guido Roberts-Borsani, Tommaso Treu, Wenlei Chen, Takahiro   
      Morishita,   
         Eros Vanzella, Adi Zitrin, Pietro Bergamini, Marco Castellano,   
         Adriano Fontana, Karl Glazebrook, Claudio Grillo, Patrick L. Kelly,   
         Emiliano Merlin, Themiya Nanayakkara, Diego Paris, Piero Rosati,   
         Lilan Yang, Ana Acebron, Andrea Bonchi, Kit Boyett, Marusa   
         Bradač, Gabriel Brammer, Tom Broadhurst, Antonello Calabro',   
         Jose M. Diego, Alan Dressler, Lukas J. Furtak, Alexei V. Filippenko,   
         Alaina Henry, Anton M. Koekemoer, Nicha Leethochawalit, Matthew   
         A. Malkan, Charlotte Mason, Amata Mercurio, Benjamin Metha,   
         Laura Pentericci, Justin Pierel, Steven Rieck, Namrata Roy, Paola   
         Santini, Victoria Strait, Robert Strausbaugh, Michele Trenti,   
         Benedetta Vulcani, Lifan Wang, Xin Wang, Rogier A. Windhorst. The   
         nature of an ultra-faint galaxy in the cosmic dark ages seen with   
         JWST. Nature, 2023; DOI: 10.1038/s41586-023-05994-w   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230601155742.htm   
      
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