If you’re in the right place on Earth and have a telescope and clear sky – or if you have a computer and online connection – you can see a rare triple transit of Jupiter’s moons Friday and into Saturday morning, January 23-24, 2015. The moons are Io, Europa and Callisto – three of Jupiter’s four large Galilean satellites – which can be seen orbiting Jupiter in an endless dance, any night, with binoculars or telescopes. What’s special here is that the moons will be positioned in such a way that their shadows will fall on Jupiter’s cloudtops. What a treat for telescopic viewers!
Bob King at skyandtelescope.com explains:
The first shadow to touch down is Callisto’s, at 9:11 p.m (CST) Friday night, followed by Io’s at 10:35 p.m., and then Europa’s nearly two hours later at 12:28 a.m. Saturday morning. All three will freckle Jupiter’s face simultaneously for just 24 minutes. At 12:52, Io’s dark pinpoint is the first to leave the stage, followed by Callisto’s, and finally Europa’s at 3:22 a.m.
The last time we in the Americas saw a triple transit like Friday’s was October 11-12, 2013. See John Rozakis’ image above. If you’re in the U.S., and you miss Friday’s event, you won’t have another chance to see something like this via telescope on U.S. soil until December 30, 2032! These events are rare. For Earth as a whole, they happen only once or twice a decade.
If you plan to observe Friday night’s triple transit telescopically, visit skyandtelescope.com for details.
If you want to observe online, keep reading …
Griffith Observatory – which created the animation of the event above – will provide a live online broadcast of the Jupiter triple-shadow transit on its Livestream channel at https://new.livestream.com/GriffithObservatoryTV.
Griffith’s webcast will begin at 8:30 p.m. PST on January 23 (0430 UTC on January 24) and conclude at 11 p.m. PST (0700 UTC). Translate to your time zone here.
A time-lapse video of the event will be available in the days that follow the event on Griffith Observatory’s YouTube channel.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.