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| Image Credit: Transits Page; Text entered by AstronomicalEventsCalendar |
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| Image Credit: The Transits Page; Text entered by AstronomicalEventsCalendar |
In the above image, you can see Io and Ganymede about to enter transit. Callisto has shifted further away from Jupiter as it completes its orbit, and Europa is shifting down, as its orbit is completed. During transits with Ganymede, because of Ganymede's orbital eccentricy, it orbits near the south pole of Jupiter, making transits involving it shorter than transits with Europa. Europa and Io orbit very closely around the belt line of Jupiter, making dual-transits more facile; Callisto only dual-transited once this year, on January 10 (which was the longest, partially becasue Callisto is the farthest moon, and orbits slower than Europa, who shared the transit. Other than that, only Io transits the rest of 2011, with either Ganymede or Europa, see for yourself here.)
Before the transit begins, at 04:19 UT, Io and Ganymede will conjunct, as the picture below (first) shows us. Celestial Coordinates: [145.1" E; 20.6" S]. On the timing of the transit, Ganymede's shadow will ingress first at 14:06 UT (note before the actual dual-transit begins), and then Io's will at 14:22, signifying the start of the dual-transit. From there, Io will start its journey across Jupiter's luminous disk at 14:29 UT, and Ganymede at 14:34, starting the dual-transit of the moons.
Here, we can clarify the terms of dual-shadow transit, and dual-transit, becasue both can happen at the same time - the October 24 and 31 transits are great examples of these (among others). A dual-shadow transit occurs when two shadows of moons travel across the surface of Jupiter together (and yes this can also happen on any other planet with two or more moons, etc.), and then, when the two moons travel together, it is called a dual-transit. (The difference is just either the shadow or moon), but both have to cross Jupiter (or any other planet, etc.) at the same time.
You can see most of the events of this transit below, computer simulated, becasue 14:22 UT is 10:22 EDT; we here in America will not be able to view this transit (neither the 31). You can convert times here. {This is a rather sad fact for us here in America, but for those in East Asia, the Pacific, and some of the Middle East will enjoy seeing this treat. Jupiter here in America is high during night - and at Opposition, and it's very sad that we won't be able to see it!}
-all pictures below are credit The Transit's Page, Galilean Moons Simulator; text entered by myself-
TOTAL EVENTS FOR OCTOBER 24, 2011
2011-Oct-24 00:16 Conjunction of Europa and Ganymede [194.4" E; 27.3" S]
2011-Oct-24 04:19 Conjunction of Io and Ganymede [145.1" E; 20.6" S]
2011-Oct-24 04:48 Transit of Great Red Spot
2011-Oct-24 05:00 Eastern Elongation of Io, 145.9"
2011-Oct-24 08:27 Eastern Elongation of Europa, 235.1"
2011-Oct-24 14:06 Shadow Transit Ingress of Ganymede
2011-Oct-24 14:22 Shadow Transit Ingress of Io (Double Shadow Transit Begin)
2011-Oct-24 14:29 Transit Ingress of Io
2011-Oct-24 14:34 Transit Ingress of Ganymede (Double Transit Begin)
2011-Oct-24 14:44 Transit of Great Red Spot
2011-Oct-24 15:16 Inferior conjunction of Ganymede
2011-Oct-24 15:20 Shadow Transit Egress of Ganymede (Double Shadow Transit End)
2011-Oct-24 15:34 Inferior conjunction of Io
2011-Oct-24 15:52 Transit Egress of Ganymede (Double Transit End)
2011-Oct-24 16:09 Conjunction of Io and Ganymede [12.5" W; 13.1" S]
2011-Oct-24 16:30 Shadow Transit Egress of Io
2011-Oct-24 16:38 Transit Egress of Io
(With thanks to Galilean moon Simulator).
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Results of the Dual-Shadow Transit
The dual-shadow transit on October 24, this past Monday was a true spectacle! Although we here in America could not view such a wonderful event, I have been able to find a few pictures scattered across the internet of this spectacular event. About the transits: "After having such a prolific season of simultaneous Jovian dual-transits last May-June, it will be hard to accept the fact that we have only two more this 2011 season: October 24, 2011 and October 31, 2011. Each transits are an exact week apart (although times differ) and both are dual-shadow transits. Io and Ganymede both partake in each event, as their orbits must be aligned perfectly just for this week." Read more at the link above.
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| This picture was taken from 'Cloudy Night Telescope Reviews' under username 'claytonbigwood' |
Below is a picture computed (simulated) by Celestia software. You can see Ganymede and Io as the light blobs, and their shadows cast on the planet. If you would to see the picture clearer, you may click on it for higher resolution.
Although these are not the most high quality images available, they do beautifully illustrate the beauty of this transit. Remember that October 31 brings us another galactic delicacy! Another dual-shadow transit awaits us...
