                        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.

                                 2026 May 21
   On a dark background, galaxies are shown as fuzzy white dots. A bright
      blue spiral expands from the center. Clicking on the picture will
             download the highest resolution version available.

                       A Collision of Galaxy Clusters
   Image Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS;
            Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds
             Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

   Explanation: This big beautiful spiral shines in X-ray light. It is
   about 20 times larger than our Galaxy. It belongs to Abell 2029, a
   galaxy cluster one billion light-years away. (To see only the galaxies,
   hover your cursor over the image, or follow this link.) Galaxy clusters
   are the largest structures in the universe that are supported by
   gravity. Abell 2029 is formed by thousands of galaxies, surrounded by a
   huge cloud of hot gas and the equivalent of hundreds of trillions times
   the mass of the Sun in dark matter. The spiral is made of gas, mostly
   hydrogen and helium, heated to tens of millions of degrees. It was
   found in a recent study that used data from NASA's Chandra X-ray
   Observatory to show that Abell 2029 had a collision with a smaller
   cluster four billion years ago. The collision affected the
   gravitational field and caused the intracluster gas to slosh, like wine
   moving in a wine glass, shaping the spiral.

                      Tomorrow's picture: stellar winds
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

