                        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.

                                 2025 May 21
      The Sun is pictured complete with active regions, filaments, and
    prominences. Down the Sun's face is a series of silhouettes that are
   the International Space Station passing right in front. Please see the
                 explanation for more detailed information.

                 International Space Station Crosses the Sun
                 Image Credit & Copyright: Pau Montplet Sanz

   Explanation: Typically, the International Space Station is visible only
   at night. Slowly drifting across the night sky as it orbits the Earth,
   the International Space Station (ISS) can be seen as a bright spot
   about once a month from many locations. The ISS is then visible only
   just after sunset or just before sunrise because it shines by reflected
   sunlight -- once the ISS enters the Earth's shadow, it will drop out of
   sight. The only occasion when the ISS is visible during the day is when
   it passes right in front of the Sun. Then, it passes so quickly that
   only cameras taking short exposures can visually freeze the ISS's
   silhouette onto the background Sun. The featured picture did exactly
   that -- it is actually a series of images taken a month ago from Sant
   Feliu de Buixalleu, Spain with perfect timing. This image series was
   later combined with a separate image highlighting the texture of the
   active Sun which included several Sun's prominences around the edge.

     Celestial Surprise: What picture did APOD feature on your birthday?
                                 (post 1995)
                       Tomorrow's picture: pluto below
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

