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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Galactic bubbles are more complex than imagined    
    Fresh look at old data reveals novel details about galactic formation   
      
      
     Date:   
         May 8, 2023   
     Source:   
         Ohio State University   
     Summary:   
         Astronomers have revealed new evidence about the properties of the   
         giant bubbles of high-energy gas that extend far above and below   
         the Milky Way galaxy's center.   
      
      
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   FULL STORY   
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   Astronomers have revealed new evidence about the properties of the giant   
   bubbles of high-energy gas that extend far above and below the Milky   
   Way galaxy's center.   
      
   In a study recently published inNature Astronomy, a team led by scientists   
   at The Ohio State University was able to show that the shells of these   
   structures -- dubbed "eRosita bubbles" after being found by the eRosita   
   X-ray telescope - are more complex than previously thought.   
      
   Although they bear a striking similarity in shape to Fermi   
   bubbles, eRosita bubbles are larger and more energetic than their   
   counterparts. Known together as the "galactic bubbles" due to their size   
   and location, they provide an exciting opportunity to study star formation   
   history as well as reveal new clues about how the Milky Way came to be,   
   said Anjali Gupta, lead author of the study and a former postdoctoral   
   researcher at Ohio State who is now a professor of astronomy at Columbus   
   State Community College.   
      
   These bubbles exist in the gas that surrounds galaxies, an area which   
   is called the circumgalactic medium.   
      
   "Our goal was really to learn more about the circumgalactic medium, a   
   place very important in understanding how our galaxy formed and evolved,"   
   Gupta said.   
      
   "A lot of the regions that we were studying happened to be in the region   
   of the bubbles, so we wanted to see how different the bubbles are when   
   compared to the regions which are away from the bubble."  Previous studies   
   had assumed that these bubbles were heated by the shock of gas as it   
   blows outward from the galaxy, but this paper's main findings suggest the   
   temperature of the gas within the bubbles isn't significantly different   
   from the area outside of it.   
      
   "We were surprised to find that the temperature of the bubble region and   
   out of the bubble region were the same," said Gupta. Additionally, the   
   study demonstrates that these bubbles are so bright because they're filled   
   with extremely dense gas, not because they are at hotter temperatures   
   than the surrounding environment.   
      
   Gupta and Smita Mathur, co-author of the study and a professor of   
   astronomy at Ohio State, did their analysis using observations made   
   by the Suzaku satellite, a collaborative mission between NASA and the   
   Japanese Aerospace Exploration Agency.   
      
   By analyzing 230 archival observations made between 2005 and 2014,   
   researchers were able to characterize the diffuse emission -- the   
   electromagnetic radiation from very low density gas -- of the galactic   
   bubbles, as well as the other hot gases that surround them.   
      
   Although the origin of these bubbles has been debated in scientific   
   literature, this study is the first that begins to settle it, said   
   Mathur. As the team found an abundance of non-solar neon-oxygen and   
   magnesium-oxygen ratios in the shells, their results strongly suggest   
   that galactic bubbles were originally formed by nuclear star-forming   
   activity, or the injection of energy by massive stars and other kinds   
   of astrophysical phenomena, rather than through the activities of a   
   supermassive black hole.   
      
   "Our data supports the theory that these bubbles are most likely formed   
   due to intense star formation activity at the galactic center, as opposed   
   to black hole activity occurring at the galactic center," Mathur said. To   
   further investigate the implications their discovery may have for other   
   aspects of astronomy, the team hopes to use new data from other upcoming   
   space missions to continue characterizing the properties of these bubbles,   
   as well as work on novel ways to analyze the data they already have.   
      
   "Scientists really do need to understand the formation of the bubble   
   structure, so by using different techniques to better our models, we'll   
   be able to better constrain the temperature and the emission measures   
   that we are looking for," said Gupta.   
      
   Other co-authors were Joshua Kingsbury and Sanskriti Das of Ohio State   
   and Yair Krongold of the National Autonomous University of Mexico. This   
   work was supported by NASA.   
      
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Galaxies # Black_Holes # Astronomy # Astrophysics #   
                   Stars # Solar_System # Extrasolar_Planets # NASA   
       * RELATED_TERMS   
             o Spitzer_space_telescope o Milky_Way o Magellanic_Clouds   
             o Local_Group o Globular_cluster o Planetary_nebula o   
             Barred_spiral_galaxy o Interstellar_medium   
      
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   Story Source: Materials provided by Ohio_State_University. Original   
   written by Tatyana Woodall. Note: Content may be edited for style   
   and length.   
      
      
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   Journal Reference:   
      1. Anjali Gupta, Smita Mathur, Joshua Kingsbury, Sanskriti Das, Yair   
         Krongold. Thermal and chemical properties of the eROSITA   
         bubbles from Suzaku observations. Nature Astronomy, 2023; DOI:   
         10.1038/s41550-023- 01963-5   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230508150940.htm   
      
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