Two of Jupiter’s moons, Io and Ganymede, will cast shadows simultaneously on the face of the biggest planet on the night of May 27-28, 2015. This will present an excellent opportunity for imagers to capture the dramatic motion of Jupiter as it goes through its perpetual Newtonian waltz with its largest moons.
The event is easily visible in Slooh telescopes. The two moons begin their encounter when the shadow of Ganymede ingresses the face of the planet on May 28 at 0:58 UT. The shadow of speedier Io, the closest moon to Jupiter, ingresses at 2:01 UT, then egresses at 4:18 UT. The shadow of Ganymede then egresses at 4:34 UT on the 28th. Shortly before each shadow transit begin, the moons themselves can be seen passing across the face of Jupiter.
Slooh members have imaged many shadow transits, including this single transit of Ganymede’s shadow on December 14, 2014.