MSGID: 1:317/3 647eb696   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Early universe crackled with bursts of star formation, Webb shows    
      
     Date:   
         June 5, 2023   
     Source:   
         NASA/Goddard Space Flight Center   
     Summary:   
         Among the most fundamental questions in astronomy is: How did the   
         first stars and galaxies form? NASA's James Webb Space Telescope   
         is already providing new insights into this question. One of   
         the largest programs in Webb's first year of science is the JWST   
         Advanced Deep Extragalactic Survey, or JADES, which will devote   
         about 32 days of telescope time to uncover and characterize faint,   
         distant galaxies. While the data is still coming in, JADES already   
         has discovered hundreds of galaxies that existed when the universe   
         was less than 600 million years old. The team also has identified   
         galaxies sparkling with a multitude of young, hot stars.   
      
      
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   FULL STORY   
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   Among the most fundamental questions in astronomy is: How did the first   
   stars and galaxies form? NASA's James Webb Space Telescope is already   
   providing new insights into this question. One of the largest programs   
   in Webb's first year of science is the JWST Advanced Deep Extragalactic   
   Survey, or JADES, which will devote about 32 days of telescope time to   
   uncover and characterize faint, distant galaxies. While the data is still   
   coming in, JADES already has discovered hundreds of galaxies that existed   
   when the universe was less than 600 million years old. The team also   
   has identified galaxies sparkling with a multitude of young, hot stars.   
      
   "With JADES, we want to answer a lot of questions, like: How did the   
   earliest galaxies assemble themselves? How fast did they form stars? Why   
   do some galaxies stop forming stars?" said Marcia Rieke of the University   
   of Arizona in Tucson, co-lead of the JADES program.   
      
   Star Factories Ryan Endsley of the University of Texas at Austin led   
   an investigation into galaxies that existed 500 to 850 million years   
   after the big bang. This was a crucial time known as the Epoch of   
   Reionization. For hundreds of millions of years after the big bang,   
   the universe was filled with a gaseous fog that made it opaque to   
   energetic light. By one billion years after the big bang, the fog   
   had cleared and the universe became transparent, a process known as   
   reionization. Scientists have debated whether active, supermassive   
   black holes or galaxies full of hot, young stars were the primary cause   
   of reionization.   
      
   As part of the JADES program, Endsley and his colleagues studied   
   these galaxies with Webb's NIRSpec (Near-Infrared Spectrograph)   
   instrument to look for signatures of star formation -- and found them in   
   abundance. "Almost every single galaxy that we are finding shows these   
   unusually strong emission line signatures indicating intense recent   
   star formation. These early galaxies were very good at creating hot,   
   massive stars," said Endsley.   
      
   These bright, massive stars pumped out torrents of ultraviolet light,   
   which transformed surrounding gas from opaque to transparent by ionizing   
   the atoms, removing electrons from their nuclei. Since these early   
   galaxies had such a large population of hot, massive stars, they may have   
   been the main driver of the reionization process. The later reuniting of   
   the electrons and nuclei produces the distinctively strong emission lines.   
      
   Endsley and his colleagues also found evidence that these young galaxies   
   underwent periods of rapid star formation interspersed with quiet periods   
   where fewer stars formed. These fits and starts may have occurred as   
   galaxies captured clumps of the gaseous raw materials needed to form   
   stars.   
      
   Alternatively, since massive stars quickly explode, they may have injected   
   energy into the surrounding environment periodically, preventing gas   
   from condensing to form new stars.   
      
   The Early Universe Revealed Another element of the JADES program involves   
   the search for the earliest galaxies that existed when the universe was   
   less than 400 million years old. By studying these galaxies, astronomers   
   can explore how star formation in the early years after the big bang was   
   different from what is seen in current times. The light from faraway   
   galaxies is stretched to longer wavelengths and redder colors by the   
   expansion of the universe -- a phenomenon called redshift.   
      
   By measuring a galaxy's redshift, astronomers can learn how far away it   
   is and, therefore, when it existed in the early universe. Before Webb,   
   there were only a few dozen galaxies observed above a redshift of 8,   
   when the universe was younger than 650 million years old, but JADES has   
   now uncovered nearly a thousand of these extremely distant galaxies.   
      
   The gold standard for determining redshift involves looking at a galaxy's   
   spectrum, which measures its brightness at a myriad of closely spaced   
   wavelengths. But a good approximation can be determined by taking photos   
   of a galaxy using filters that each cover a narrow band of colors to get a   
   handful of brightness measurements. In this way, researchers can determine   
   estimates for the distances of many thousands of galaxies at once.   
      
   Kevin Hainline of the University of Arizona in Tucson and his colleagues   
   used Webb's NIRCam (Near-Infrared Camera) instrument to obtain these   
   measurements, called photometric redshifts, and identified more than   
   700 candidate galaxies that existed when the universe was between   
   370 million and 650 million years old. The sheer number of these   
   galaxies was far beyond predictions from observations made before   
   Webb's launch. The observatory's exquisite resolution and sensitivity   
   are allowing astronomers to get a better view of these distant galaxies   
   than ever before.   
      
   "Previously, the earliest galaxies we could see just looked like little   
   smudges. And yet those smudges represent millions or even billions of   
   stars at the beginning of the universe," said Hainline. "Now, we can see   
   that some of them are actually extended objects with visible structure. We   
   can see groupings of stars being born only a few hundred million years   
   after the beginning of time."  "We're finding star formation in the   
   early universe is much more complicated than we thought," added Rieke.   
      
   These results are being reported at the 242nd meeting of the American   
   Astronomical Society in Albuquerque, New Mexico.   
      
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Galaxies # Astrophysics # Stars # Big_Bang # Cosmology #   
                   Extrasolar_Planets # Astronomy # Black_Holes   
       * RELATED_TERMS   
             o Hubble_Deep_Field o Supergiant o Galaxy   
             o Large-scale_structure_of_the_cosmos   
             o Galaxy_formation_and_evolution o Radio_telescope o   
             Edwin_Hubble o Astrophysics   
      
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   Story Source: Materials provided by   
   NASA/Goddard_Space_Flight_Center. Note: Content may be edited for style   
   and length.   
      
      
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230605181111.htm   
      
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