June 24, 2018

Astro-Challenge: See the Galilean Moons in 1,2,3,4 Order.

Astronomy is chock full of alignments, synchronizations, and oddities that happen on variable cycles. This week, I’d like to point you towards one of those gee-whiz occurrences that happens early Friday morning. On May 28th, 2010, you’ll have the opportunity to view Jupiter’s classical four Galilean Moons in one-through-four order, all positioned on one side of the planet. This would also make for an interesting “family portrait” of the set. Jupiter is in dawn skies, currently rising about 4 hours prior to the Sun. The window of time is short; the moons are only in this arrangement from 06:33 UT until 07:50 UT, and “Jupiter-rise” for folks in the US Eastern time zone only occurs at about 0:700 UT (about 3 AM EDT local). Hence, only folks positioned in the Eastern and Atlantic time zones will have a shot at catching this alignment under dark skies.

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