Griffith Observatory | 2015 Jan 22
A rare celestial event will take place on Friday night, January 23, 2015, when the shadows of three of Jupiter’s four largest moons will fall upon Jupiter at the same time. The shadows of these three moons – Io, Europa, and Callisto – will cross Jupiter’s disk throughout the evening. The moons will also cross in front of the planet. Galileo discovered these moons, and one more, Ganymede, in 1610. Ganymede will also be visible on January 23, but unlike the others it will not cast a shadow on Jupiter. Three moon shadows will not appear simultaneously on Jupiter again, from Los Angeles, until 2032.Animation of Jupiter Triple Moon Shadow Transit, January 23, 2015
Callisto’s shadow is the first to appear on Jupiter, at 7:11 p.m. PST. Io’s shadow joins it at 8:35 p.m., PST. The triple-shadow transit begins when Europa’s shadow joins the other two at 10:27 p.m., PST, and concludes when Io’s shadow moves past Jupiter at 10:52 p.m., PST. Callisto’s and Europa’s shadows move off of Jupiter’s disk at 12:00 midnight PST, and 1:22 a.m. PST (January 24), respectively.
As if the triple-shadow transit weren’t enough, another rare Jupiter shadow event precedes it. Io will begin to cross in front of Jupiter’s disk at 8:54 p.m., PST, 19 minutes after its shadow. At 9:40 p.m., PST, swiftly-moving Io will be eclipsed as it runs into the shadow of slower-moving Callisto. This will darken Io, and make it suddenly conspicuous as a black dot against the bright clouds of Jupiter. Io’s shadow on the planet will merge with Callisto’s shadow for 19 minutes. Then, Io will again become visible at 10:12 p.m., PST, when it appears as a bright speck in front of Callisto’s giant shadow.
Griffith Observatory will provide a live video stream of the Jupiter triple-shadow transit. The webcast will begin at 8:30 p.m., and conclude at 11:00 p.m. ...