                        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 October 31

                     Dark Matter in a Simulated Universe
   Illustration Credit & Copyright: Tom Abel & Ralf Kaehler (KIPAC, SLAC),
                                    AMNH

   Explanation: Is our universe haunted? It might look that way on this
   dark matter map. The gravity of unseen dark matter is the leading
   explanation for why galaxies rotate so fast, why galaxies orbit
   clusters so fast, why gravitational lenses so strongly deflect light,
   and why visible matter is distributed as it is both in the local
   universe and on the cosmic microwave background. The featured image
   from the American Museum of Natural History's Hayden Planetarium Space
   Show Dark Universe highlights one example of how pervasive dark matter
   might haunt our universe. In this frame from a detailed computer
   simulation, complex filaments of dark matter, shown in black, are
   strewn about the universe like spider webs, while the relatively rare
   clumps of familiar baryonic matter are colored orange. These
   simulations are good statistical matches to astronomical observations.
   In what is perhaps a scarier turn of events, dark matter -- although
   quite strange and in an unknown form -- is no longer thought to be the
   strangest source of gravity in the universe. That honor now falls to
   dark energy, a more uniform source of repulsive gravity that seems to
   now dominate the expansion of the entire universe.

                Not only Halloween: Today is Dark Matter Day.
                   Tomorrow's picture: waterfall milky way
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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.

