                        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 March 9

                              DART vs Dimorphos
                 Image Credit: NASA, Johns Hopkins APL, DART

   Explanation: On the first planetary defense test mission from planet
   Earth, the DART spacecraft captured this close-up on 26 September 2022,
   three seconds before slamming into the surface of asteroid moonlet
   Dimorphos. The spacecraft's outline with two long solar panels is
   traced at its projected point of impact between two boulders. The
   larger boulder is about 6.5 meters across. While the DART (Double
   Asteroid Redirection Test) spacecraft had a mass of some 570 kilograms,
   the estimated mass of Dimorphos, the smaller member of a near-Earth
   binary asteroid system, was about 5 billion kilograms. The direct
   kinetic impact of the spacecraft measurably altered the speed of
   Dimorphos by a fraction of a percent, reducing its 12 hour orbital
   period around its larger companion asteroid 65803 Didymos by about 33
   minutes. Beyond successfully demonstrating a technique to change an
   asteroid's orbit that can prevent future asteroid strikes on planet
   Earth, the planetary-scale impact experiment has given the
   150-meter-sized Dimorphos a comet-like tail of material.

                     Tomorrow's picture: a great nebula
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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.

