                        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 May 28
   A pair of asteroids are shown with a large, elongated and cratered one
     on the left and a much smaller one on the far right. Please see the
                 explanation for more detailed information.

                      Ida and Dactyl: Asteroid and Moon
                  Image Credit: NASA, JPL, Galileo Mission

   Explanation: This asteroid has a moon. The robot spacecraft Galileo on
   route to Jupiter in 1993 encountered and photographed two asteroids
   during its long interplanetary voyage. The second minor planet it
   photographed, 243 Ida, was unexpectedly discovered to have a moon. The
   tiny moon, Dactyl, is only about 1.6 kilometers across and seen as a
   small dot on the right of the sharpened featured image. In contrast,
   the potato-shaped Ida is much larger, measuring about 60 kilometers
   long and 25 km wide. Dactyl is the first moon of an asteroid ever
   discovered -- now many asteroids are known to have moons. The names Ida
   and Dactyl are from Greek mythology.

                      Tomorrow's picture: sea blue sky
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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,
                           NASA Science Activation
                             & Michigan Tech. U.

