                        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 May 4
    A picture of the International Space Station crossing the Sun. Please
             see the explanation for more detailed information.

                    Space Station, Solar Prominences, Sun
                  Image Credit & Copyright: Mehmet Ergun

   Explanation: That's no sunspot. It's the International Space Station
   (ISS) caught passing in front of the Sun. Sunspots, individually, have
   a dark central umbra, a lighter surrounding penumbra, and no Dragon
   capsules attached. By contrast, the ISS is a complex and multi-spired
   mechanism, one of the largest and most complicated spacecraft ever
   created by humanity. Also, sunspots circle the Sun, whereas the ISS
   orbits the Earth. Transiting the Sun is not very unusual for the ISS,
   which orbits the Earth about every 90 minutes, but getting one's
   location, timing and equipment just right for a great image is rare.
   The featured picture combined three images all taken from the same
   location and at nearly the same time. One image -- overexposed --
   captured the faint prominences seen across the top of the Sun, a second
   image -- underexposed -- captured the complex texture of the Sun's
   chromosphere, while the third image -- the hardest to get -- captured
   the space station as it shot across the Sun in a fraction of a second.
   Close inspection of the space station's silhouette even reveals a
   docked Dragon Crew capsule.

                      Tomorrow's picture: all sky STEVE
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