June 2022    
         
         
 
     
  Backyard black hole  
     
  Scientists believe that most galaxies contain a supermassive black hole at their center. Our Milky Way monster is called Sagittarius A* or Sgr A* (pronounced sadge-ay-star). And it’s kind of a baby: only a few million times the mass of the sun compared to the 6.5 billion solar masses of M87*, the first black hole ever photographed. Sgr A* is also a picky eater and can’t sit still long enough for a good picture. It takes a talented photographer to get that perfect shot.  
     
  Visualizing the void  
     
 
Photograph of Sgr A star
 
 
     
  It’s impossible to see a black hole, but astronomers can capture the light bent by its powerful gravity—thus revealing the black hole’s shadow. (ESO/EHT Collaboration, CC BY 4.0)  
     
 
     
  In 2019 the Event Horizon Telescope Collaboration, which includes the UChicago-led South Pole Telescope, released the first photograph of a black hole. Last month they unveiled another: a portrait of Sagittarius A*, the supermassive black hole at the center of the Milky Way.  
     
 
  Daniel Holz, SM’94, PhD’98, an expert on black holes, and John Carlstrom, director of the South Pole Telescope, describe the quest to photograph Sgr A*.  
 
       
  Until now astronomers have only inferred the existence of our supermassive black hole by studying the behavior of nearby stars. This image provides the first direct visual evidence.  
     
 
 
  Dense information  
     
 
     
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UChicago Laboratory Schools alumna Andrea Ghez received the 2020 Nobel Prize in Physics for her work studying Sgr A*.
 
     
     
     
 
     
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Supermassive black holes existed when the universe was still young, but it takes time for black holes to grow that big. Maybe they had a dark matter diet.
 
     
     
     
 
     
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Before we saw black holes, we heard them.
 
     
     
 
         
         
    Spotlight    
         
         
 
     
  Virtually possible  
     
 
Video about EHT
 
 
  How do you build an observatory the size of the earth? With a wide scope.  
     
  The Event Horizon Telescope is a global network of linked radio dishes that together form a virtual, planet-sized interferometer, capable of imaging the darkest objects in the universe.  
     
 
 
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