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.

                               2020 October 25

                     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
   previous 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.

                      Tomorrow's picture: spooky space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.


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