Some natural phenomena need few words to explain why they're fascinating. Eclipses, transits, and phases in astronomy tend to fall into that category. Here's a stunning sequence of images captured by the Hubble Space Telescope's Wide Field Camera 3 showing the triple conjunction and transit of the large Jovian moons Europa, Callisto, and Io over some 42 minutes in January 2015.
A triple transit
Jupiter of course has a lot of moons, 67 confirmed ones in fact. Some of these smaller ones were in on the act too, they're just too small to notice easily. Here's a guide to the position of 2 others - Thebe and Amalthea.
Two more transiting moons...(NASA/ESA)
So in fact this was a quintuple conjunction event!
And finally, in animated form.
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ABOUT THE AUTHOR(S)
Caleb A. Scharf
Dr. Caleb A. Scharf is Director of Astrobiology at Columbia University,and has an international reputation as a research astrophysicist, and asa lecturer to college and public audiences. The UK's Guardian newspaperhas listed his blog Life, Unbounded, as one of their "hottest scienceblogs," while an editor at Seed Magazine called it "phenomenal.Informed, fresh, and thoughtful." Scharf is author and co-author of morethan 100 scientific research articles in astronomy and astrophysics. Hiswork has been featured in publications such as New Scientist, ScientificAmerican, Science News, Cosmos Magazine, Physics Today, and NationalGeographic, as well as online at sites like Space.com and Physorg.com.His textbook for undergraduate and graduate students, Extrasolar Planetsand Astrobiology, won the 2012 Chambliss Prize of the AAS. Hisarticles and reviews have appeared in such prestigious publications asScience, Nature, The Astrophysical Journal, and Monthly Notices of theRoyal Astronomical Society.Dr. Scharf is a regular keynote speaker at academic meetings, such asfor the American Physical Society, museums, and both public and privatevenues, including the American Museum of Natural History, the RubinMuseum of Art in New York. He has been a guest on Krulwich on Science atNPR, William Shatner's "Weird or What?" and has served as a consultantto editors and producers at National Geographic Magazine, The ScienceChannel, The Discovery Channel, and The New York Times.