Image Credit & Copyright: NASA/ESA Hubble Space Telescope.
On January 24, 2015 something happened on Jupiter that we won’t have the ability to see again until 2032; a triple Galilean moon shadow transit across the face of Jupiter. The show began with the shadow of Io and the little moon itself (small shadow and small yellow moon at right) then quickly behind that was Callisto’s shadow almost coming into view underneath Io while Callisto trailed behind quite a ways (large brown moon at bottom left). Just beyond that and completing the triple transit is that shadow of Europa seen here just breaking into view at the bottom left of the image. Europa itself would soon cross the face of the Jovian planet as well making a triple shadow and moon transit which for us amateurs equates to one hell of a show if you were fortunate enough to have clean non-turbulent skies.
If you’ve missed this event there’s still time to catch some great Galilean moon sites as it’s “Mutual Event Season” on Jupiter. That’s a roughly six year event where the four big moons interact visually and over the course of 6 months or so (Nov-May) you will be able to watch them occult and eclipse eachother which is fantastic when you watch it in real time. Here’s the writeup I did on Jupiter’s opposition and a brief description of the mutual event phenomenon. The events that I have listed were for January but in the links at the bottom of the post you can dig through and find exactly when you will be able to catch some.
NASA Hubble News Center page for this image: http://hubblesite.org/newscenter/archive/releases/2015/05/image/e/
ESA Hubble Space Telescope page for this image: http://www.spacetelescope.org/news/heic1504/