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                        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.

                                2023 June 29
    The illustration shows the beams from pulsars around the image and a
     pair of merging black holes on the upper left. A grid depicting the
   warping of spacetime by passing gravitational waves spreads across the
   image center. Please see the explanation for more detailed information.

                  A Message from the Gravitational Universe
    Illustration Credit: NANOGrav Physics Frontier Center; Text: Natalia
                          Lewandowska (SUNY Oswego)

   Explanation: Monitoring 68 pulsars with very large radio telescopes,
   the North American Nanohertz Observatory for Gravitational Waves
   (NANOGrav) has uncovered evidence for the gravitational wave (GW)
   background by carefully measuring slight shifts in the arrival times of
   pulses. These shifts are correlated between different pulsars in a way
   that indicates that they are caused by GWs. This GW background is
   likely due to hundreds of thousands or even millions of supermassive
   black hole binaries. Teams in Europe, Asia and Australia have also
   independently reported their results today. Previously, the LIGO and
   Virgo detectors have detected higher-frequency GWs from the merging of
   individual pairs of massive orbiting objects, such as stellar-mass
   black holes. The featured illustration highlights this
   spacetime-shaking result by depicting two orbiting supermassive black
   holes and several of the pulsars that would appear to have slight
   timing shifts. The imprint these GWs make on spacetime itself is
   illustrated by a distorted grid.

      Open Science: Browse 3,000+ codes in the Astrophysics Source Code
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                      Tomorrow's picture: asteroid day
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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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