                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                2021 June 30

                  Simulation: Formation of the First Stars
                Video Credit: Harley Katz (U. Oxford) et al.

   Explanation: How did the first stars form? To help find out, the SPHINX
   computer simulation of star formation in the very early universe was
   created, some results of which are shown in the featured video. Time
   since the Big Bang is shown in millions of years on the upper left.
   Even 100 million years after the Big Bang, matter was spread too
   uniformly across the cosmos for stars to be born. Besides background
   radiation, the universe was dark. Soon, slight matter clumps rich in
   hydrogen gas begin to coalesce into the first stars. In the time-lapse
   video, purple denotes gas, white denotes light, and gold shows
   radiation so energetic that it ionizes hydrogen, breaking it up into
   charged electrons and protons. The gold-colored regions also track the
   most massive stars that die with powerful supernovas. The inset circle
   highlights a central region that is becoming a galaxy. The simulation
   continues until the universe was about 550 million years old. To assess
   the accuracy of the SPHINX simulations and the assumptions that went
   into them, the results are not only being compared to current deep
   observations, but will also be compared with more direct observations
   of the early universe planned with NASA's pending James Web Space
   Telescope.

                       Tomorrow's picture: open space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

