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 April 11

                          When Black Holes Collide
    Video Credit & Copyright: Simulating Extreme Spacetimes Collaboration

   Explanation: What happens when two black holes collide? This extreme
   scenario occurs in the centers of many merging galaxies and multiple
   star systems. The featured video shows a computer animation of the
   final stages of such a merger, while highlighting the gravitational
   lensing effects that would appear on a background starfield. The black
   regions indicate the event horizons of the dynamic duo, while a
   surrounding ring of shifting background stars indicates the position of
   their combined Einstein ring. All background stars not only have images
   visible outside of this Einstein ring, but also have one or more
   companion images visible on the inside. Eventually the two black holes
   coalesce. The end stages of such a merger is now known to produce a
   strong blast of gravitational radiation, providing a new way to see our
   universe.

                    This Week is: Black Hole Week at NASA
                   Tomorrow's picture: flame without fire
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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.

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