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.

                               2019 October 6

                            The Horsehead Nebula
                Image Credit & Copyright: Jos+¬ Jim+¬nez Priego

   Explanation: The Horsehead Nebula is one of the most famous nebulae on
   the sky. It is visible as the dark indentation to the red emission
   nebula in the center of the above photograph. The horse-head feature is
   dark because it is really an opaque dust cloud that lies in front of
   the bright red emission nebula. Like clouds in Earth's atmosphere, this
   cosmic cloud has assumed a recognizable shape by chance. After many
   thousands of years, the internal motions of the cloud will surely alter
   its appearance. The emission nebula's red color is caused by electrons
   recombining with protons to form hydrogen atoms. On the image left is
   the Flame Nebula, an orange-tinged nebula that also contains filaments
   of dark dust. Just to the lower left of the Horsehead nebula featured
   picture is a blueish reflection nebulae that preferentially reflects
   the blue light from nearby stars.

                     Tomorrow's picture: jupiter spotted
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