Astronomy Picture of the Day

   [1]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 July 17
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                           Alphonsus and Arzachel
                Image Credit & [3]Copyright: [4]Noel Donnard

   Explanation: [5]Point your telescope at tonight's first quarter Moon.
   [6]Along the terminator, the shadow line between night and day, you
   might find these two large craters staring back at you with [7]an
   owlish gaze. [8]Alphonsus (left) and [9]Arzachel are ancient impact
   craters on the north eastern shores of Mare Nubium, the lunar Sea of
   Clouds. The larger Alphonsus is over 100 kilometers in diameter. A low
   sun angle highlights the crater's sharp 1.5 kilometer high central peak
   in bright sunlight and dark shadow. Scouting for potential Apollo moon
   landing sites, the [10]Ranger 9 spacecraft returned closeup photographs
   of Alphonsus before it crashed in the crater just northeast (left) of
   its central mountain in 1965. [11]Alpetragius, between Alphonsus and
   Arzachel, is the small crater with the deeply shadowed floor and overly
   large central peak.

              Tomorrow's picture: 2.5 million light-years away
     __________________________________________________________________

      [12]< | [13]Archive | [14]Submissions | [15]Index | [16]Search |
   [17]Calendar | [18]RSS | [19]Education | [20]About APOD | [21]Discuss |
                                    [22]>
     __________________________________________________________________

    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Phillip Newman [27]Specific rights apply.
              [28]NASA Web Privacy Policy and Important Notices
                A service of: [29]ASD at [30]NASA / [31]GSFC
                           & [32]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2107/AlphonseArzachelOwl_Donnard.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.astrobin.com/users/Tino2329/
   5. https://www.astrobin.com/3sjnkh/B/
   6. https://apod.nasa.gov/apod/ap070209.html
   7. https://en.wikipedia.org/wiki/Lunar_pareidolia
   8. https://en.wikipedia.org/wiki/Alphonsus_(crater)
   9. https://en.wikipedia.org/wiki/Arzachel_(crater)
  10. https://solarsystem.nasa.gov/missions/ranger-9/in-depth/
  11. https://en.wikipedia.org/wiki/Alpetragius_(crater)
  12. https://apod.nasa.gov/apod/ap210716.html
  13. https://apod.nasa.gov/apod/archivepix.html
  14. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  15. https://apod.nasa.gov/apod/lib/aptree.html
  16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  17. https://apod.nasa.gov/apod/calendar/allyears.html
  18. https://apod.nasa.gov/apod.rss
  19. https://apod.nasa.gov/apod/lib/edlinks.html
  20. https://apod.nasa.gov/apod/lib/about_apod.html
  21. http://asterisk.apod.com/discuss_apod.php?date=210717
  22. https://apod.nasa.gov/apod/ap210718.html
  23. http://www.phy.mtu.edu/faculty/Nemiroff.html
  24. http://www.phy.mtu.edu/
  25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  26. http://www.astro.umd.edu/
  27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  28. https://www.nasa.gov/about/highlights/HP_Privacy.html
  29. https://astrophysics.gsfc.nasa.gov/
  30. https://www.nasa.gov/
  31. https://www.nasa.gov/centers/goddard/
  32. http://www.mtu.edu/