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 August 21
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      Triple Transit and Mutual Events
               Image Credit & [3]Copyright: [4]Christopher Go

   Explanation: These three panels feature the Solar System's ruling
   [5]gas giant Jupiter on August 15 as seen from Cebu City, Phillipines,
   planet Earth. On that date the [6]well-timed telescopic views detail
   some remarkable performances, transits and mutual events, by Jupiter's
   Galilean moons. In the top panel, [7]Io is just disappearing into
   Jupiter's shadow at the far right, but the three other large Jovian
   moons appear against the [8]planet's banded disk. Brighter [9]Europa
   and darker [10]Ganymede are at the far left, also casting their two
   shadows on the gas giant's cloud tops. [11]Callisto is below and right
   near the planet's edge, the three moons in a triple transit across the
   face of Jupiter. Moving to the middle panel, shadows of Europa and
   Ganymede are still visible near center but Ganymede has occulted or
   passed in front of Europa. The bottom panel captures a rare view of
   Jovian moons in eclipse while transiting Jupiter, Ganymede's shadow
   falling on Europa itself. From planet Earth's perspective, similar
   mutual events, when Galilean moons occult and eclipse each other, can
   be seen every six years or so when [12]Jupiter is near its own equinox.

                       Tomorrow's picture: RS Ophiuchi
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    Authors & editors: [24]Robert Nemiroff ([25]MTU) & [26]Jerry Bonnell
                                 ([27]UMCP)
          NASA Official: Phillip Newman [28]Specific rights apply.
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                A service of: [30]ASD at [31]NASA / [32]GSFC
                           & [33]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2108/j20210815a_cgo.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. http://astro.christone.net/
   5. https://solarsystem.nasa.gov/planets/jupiter/overview/
   6. http://astro.christone.net/jupiter/index.htm
   7. https://solarsystem.nasa.gov/moons/jupiter-moons/io/in-depth/
   8. https://skyandtelescope.org/astronomy-news/jupiter-dazzles-opposition/
   9. https://www.nasa.gov/feature/jpl/a-few-steps-closer-to-europa-spacecraft-hardware-makes-headway
  10. https://www.nasa.gov/feature/jpl/ride-with-juno-as-it-flies-past-the-solar-system-s-biggest-moon-and-jupiter
  11. https://photojournal.jpl.nasa.gov/target/Callisto
  12. https://earthsky.org/astronomy-essentials/jupiter-equinox-mutual-events-moon-2021/
  13. https://apod.nasa.gov/apod/ap210820.html
  14. https://apod.nasa.gov/apod/archivepix.html
  15. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  16. https://apod.nasa.gov/apod/lib/aptree.html
  17. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  18. https://apod.nasa.gov/apod/calendar/allyears.html
  19. https://apod.nasa.gov/apod.rss
  20. https://apod.nasa.gov/apod/lib/edlinks.html
  21. https://apod.nasa.gov/apod/lib/about_apod.html
  22. http://asterisk.apod.com/discuss_apod.php?date=210821
  23. https://apod.nasa.gov/apod/ap210822.html
  24. http://www.phy.mtu.edu/faculty/Nemiroff.html
  25. http://www.phy.mtu.edu/
  26. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  27. http://www.astro.umd.edu/
  28. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  29. https://www.nasa.gov/about/highlights/HP_Privacy.html
  30. https://astrophysics.gsfc.nasa.gov/
  31. https://www.nasa.gov/
  32. https://www.nasa.gov/centers/goddard/
  33. http://www.mtu.edu/