Home > Stargazing > Jupiter Triple-Transit 11-12 October 2013

Jupiter Triple-Transit 11-12 October 2013

This post is based on a great article by Bob King on Universe Today, titled “Observing Alert: Rare Triple Transit Of Jupiter’s Moons Happens Friday Night (Oct. 11-12)”. Read that article to get the whole story!

UK stargazers can see a rare triple transit of three of Jupiter’s largest moons in the early hours of this Saturday 12 October 2013.

Every so often one of Jupiter’s largest four moons – the Galilean satellites Io, Europa, Ganymede, and Callisto – passes directly in front of the planet Jupiter casting a shadow which can be seen as a tiny black dot through even a modest telescope. This weekend three out of the four Galilean moons are casting such shadows, and from the UK you can watch the whole thing unfold between 0412 and dawn twilight, which occurs between 0600 and 0630 for most of the UK, depending on where you’re observing from (southern stargazers will have an earlier dawn brightening than their northern counterparts).

Here’s the timetable of events, based on the timings in Bob King’s article:

Saturday 12 October:
0412 BST Callisto begins to cast the first shadow
0424 BST Europa adds a second shadow
0532 BST Io adds the third shadow, and the triple transit will last until the sky brightens.

Jupiter will be high in the south-east at this time, in the constellation of Gemini. You won’t struggle to find it; it will be the brightest thing in the entire sky, shining at magnitude -1.8.

Screen Shot 2013-10-08 at 20.04.00

Location of Jupiter at 0412 on Saturday 12 October, from Stellarium

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