MSGID: 1:317/3 642e4af2   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Hubble unexpectedly finds double quasar in distant universe    
      
     Date:   
         April 5, 2023   
     Source:   
         NASA/Goddard Space Flight Center   
     Summary:   
         The early universe was a rambunctious place where galaxies often   
         bumped into each other and even merged together. Using NASA's Hubble   
         Space Telescope and other space and ground-based observatories,   
         astronomers investigating these developments have made an unexpected   
         and rare discovery: a pair of gravitationally bound quasars, both   
         blazing away inside two merging galaxies. They existed when the   
         universe was just 3 billion years old.   
      
      
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   FULL STORY   
   ==========================================================================   
   The early universe was a rambunctious place where galaxies often bumped   
   into each other and even merged together. Using NASA's Hubble Space   
   Telescope and other space and ground-based observatories, astronomers   
   investigating these developments have made an unexpected and rare   
   discovery: a pair of gravitationally bound quasars, both blazing away   
   inside two merging galaxies.   
      
   They existed when the universe was just 3 billion years old.   
      
      
   ==========================================================================   
   Quasars are bright objects powered by voracious, supermassive black holes   
   blasting out ferocious fountains of energy as they engorge themselves   
   on gas, dust, and anything else within their gravitational grasp.   
      
   "We don't see a lot of double quasars at this early time in the   
   universe. And that's why this discovery is so exciting," said graduate   
   student Yu-Ching Chen of the University of Illinois at Urbana-Champaign,   
   lead author of this study.   
      
   Finding close binary quasars is a relatively new area of research that   
   has just developed in the past 10 to 15 years. Today's powerful new   
   observatories have allowed astronomers to identify instances where two   
   quasars are active at the same time and are close enough that they will   
   eventually merge.   
      
   There is increasing evidence that large galaxies are built up through   
   mergers.   
      
   Smaller systems come together to form bigger systems and ever larger   
   structures. During that process there should be pairs of supermassive   
   black holes formed within the merging galaxies. "Knowing about the   
   progenitor population of black holes will eventually tell us about the   
   emergence of supermassive black holes in the early universe, and how   
   frequent those mergers could be," said Chen.   
      
   "We're starting to unveil this tip of the iceberg of the early binary   
   quasar population," said Xin Liu of the University of Illinois at   
   Urbana-Champaign.   
      
   "This is the uniqueness of this study. It is actually telling us that this   
   population exists, and now we have a method to identify double quasars   
   that are separated by less than the size of a single galaxy."  This was   
   a needle-in-haystack search that required the combined power of NASA's   
   Hubble Space Telescope and the W.M. Keck Observatories in Hawaii. Multi-   
   wavelength observations from the International Gemini Observatory in   
   Hawaii, NSF's Karl G. Jansky Very Large Array in New Mexico, and NASA's   
   Chandra X-ray Observatory also contributed to understanding the dynamic   
   duo. And, ESA (European Space Agency)'s Gaia space observatory helped   
   identify this double quasar in the first place.   
      
   "Hubble's sensitivity and resolution provided pictures that allow us to   
   rule out other possibilities for what we are seeing," said Chen. Hubble   
   shows, unequivocally, that this is indeed a genuine pair of supermassive   
   black holes, rather than two images of the same quasar created by a   
   foreground gravitational lens. And, Hubble shows a tidal feature from   
   the merging of two galaxies, where gravity distorts the shape of the   
   galaxies forming two tails of stars.   
      
   However, Hubble's sharp resolution alone isn't good enough to go looking   
   for these dual light beacons. The researchers enlisted Gaia, which   
   launched in 2013, to pinpoint potential double-quasar candidates. Gaia   
   measures the positions, distances, and motions of nearby celestial   
   objects very precisely.   
      
   But in a novel technique, it can be used to explore the distant universe.   
      
   Gaia's huge database can be used to search for quasars that mimic the   
   apparent motion of nearby stars. The quasars appear as single objects   
   in the Gaia data because they are so close together. However, Gaia can   
   pick up a subtle, unexpected "jiggle" that mimics an apparent change in   
   position of some of the quasars it observes.   
      
   In reality, the quasars aren't moving through space in any measurable way.   
      
   Instead, their jiggle could be evidence of random fluctuations of light   
   as each member of the quasar pair varies in brightness on timescales of   
   days to months, depending on their black hole's feeding schedule. This   
   alternating brightness between the quasar pair is similar to seeing a   
   railroad crossing signal from a distance. As the lights on both sides of   
   the stationary signal alternately flash, the sign gives the illusion of   
   "jiggling."  Another challenge is that because gravity warps space like a   
   funhouse mirror, a foreground galaxy could split the image of a distant   
   quasar into two, creating the illusion it was really a binary pair. The   
   Keck telescope was used to make sure there's no lensing galaxy in between   
   us and the suspected double quasar.   
      
   Because Hubble peers into the distant past, this double quasar no longer   
   exists. Over the intervening 10 billion years, their host galaxies have   
   likely settled into a giant elliptical galaxy, like the ones seen in the   
   local universe today. And, the quasars have merged to become a gargantuan,   
   supermassive black hole at its center. The nearby giant elliptical galaxy,   
   M87, has a monstrous black hole weighing 6.5 billion times the mass of   
   our Sun.   
      
   Perhaps this black hole was grown from one or more galaxy mergers over   
   the past billions of years.   
      
   The upcoming NASA Nancy Grace Roman Space Telescope, having the same   
   visual acuity as Hubble, is ideal for binary quasar hunting. Hubble has   
   been used to painstakingly take data for individual targets. But Roman's   
   very wide-angle infrared view of the universe is 200 times larger than   
   Hubble's. "A lot of quasars out there could be binary systems. The Roman   
   telescope can do huge improvements in this research area," said Liu.   
      
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Black_Holes # Space_Telescopes # Astronomy #   
                   Astrophysics # Galaxies # NASA # Space_Exploration #   
                   Cosmology   
       * RELATED_TERMS   
             o Hubble_Deep_Field o Compton_Gamma_Ray_Observatory   
             o Edwin_Hubble o Spitzer_space_telescope o Galaxy o   
             Radio_telescope o Large-scale_structure_of_the_cosmos o   
             Galaxy_formation_and_evolution   
      
   ==========================================================================   
   Story Source: Materials provided by   
   NASA/Goddard_Space_Flight_Center. Note: Content may be edited for style   
   and length.   
      
      
   ==========================================================================   
   Related Multimedia:   
       *   
       Artist's_concept_shows_brilliant_glare_of_two_quasars_residing_in_cores   
         of_two_galaxies_that_are_in_the_chaotic_process_of_merging   
   ==========================================================================   
   Journal Reference:   
      1. Yu-Ching Chen, Xin Liu, Adi Foord, Yue Shen, Masamune Oguri,   
      Nianyi Chen,   
         Tiziana Di Matteo, Miguel Holgado, Hsiang-Chih Hwang, Nadia   
         Zakamska. A close quasar pair in a disk-disk galaxy merger at z =   
         2.17. Nature, 2023; 616 (7955): 45 DOI: 10.1038/s41586-023-05766-6   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230405130135.htm   
      
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