Tuesday, January 10, 2012

Jovian Dual-Shadow Transit of January 11, 2012

2012. It is a new year, and what better other way is it to start it off with another dual-shadow transit of Ganymede and Europa!? Although 2012 has less dual-transits than 2011 had, hopefully this year will exceed your expectation on astronomy and Jovian-dual transits. We start the year with a dual-shadow transit of Europa and Ganymede on January 11, 2012 at 4:41 UT. Io will not come into the picture again until March 23; Europa and Ganymede will dual-shadow transit three times in January (the 11, 18 & 25). Callisto does not take any part this year, as it did on January 25, 2011.

According to Simultaneous Transits of Galilean satellites and their shadows across Jupiter during 2012, a paper that lists each of dual-transit phenomena in full (can be accessed here), the January 11 dual-shadow transit is one of the shortest transits of the year, with Europa and Ganymede themselves transiting for 00:23 minutes; both shadows of these moons transit for 00:20 minutes, though. This occurs over the time frame of 06:24 to 06:47 UT for dual-transit, and 06:25 to 06:25 UT for dual-shadow transit. If the skies are clear on the Eastern Seaboard, this event will take place at 1:24 am EST and end on 1:47 am EST. The last two transits (October 24 and 31) were not visible; at last there is one that is, needless to consider others that are coming!

Note: If something on the picture reads "Shadow Ingress (or Egress)," and no shadow is seen, this is particularly because of Jupiter's position at this time. The shadows will not be visible until Jupiter moves into another position. 

-all pictures below are credit The Transit's Page, Galilean Moons Simulator; text entered by myself-

January 10, 2012 at 21:24 UT. You can see that Ganymede and Europa are ready to transit 1/11 at approx. 4:30 UT!

Here Comes Io! Although the above pictures are cropped, Io is in them to the right of Jupiter. Now, it has come in full view as it ascends into occultation by Jupiter itself. Ganymede and Io conjunct right before this occurs, as you can see. 

2012-Jan-11 16:54 Conjunction of Europa and Ganymede [124.5" W; 6.4" S]
You may notice that Europa and Ganymede conjunct twice today (at 16:54 and 19:33). This is becasue of their orbits. They are, in the above picture, practically at the end of their 'orbit,' and will reverse to come behind Jupiter. Doing this, they conjunct again.


2012-Jan-11 04:39 Transit Ingress of Ganymede
2012-Jan-11 04:41 Shadow Transit Ingress of Ganymede
2012-Jan-11 05:05 Transit of Great Red Spot
2012-Jan-11 05:45 Inferior conjunction of Ganymede
2012-Jan-11 06:24 Transit Ingress of Europa (Double Transit Begin)
2012-Jan-11 06:25 Shadow Transit Ingress of Europa (Double Shadow Transit Begin)
2012-Jan-11 06:45 Shadow Transit Egress of Ganymede (Double Shadow Transit End)
2012-Jan-11 06:47 Transit Egress of Ganymede (Double Transit End)
2012-Jan-11 07:29 Conjunction of Io and Ganymede [19.9" W; 22.2" S]
2012-Jan-11 07:29 Occultation Disappearance of Io
2012-Jan-11 07:40 Inferior conjunction of Europa
2012-Jan-11 08:52 Shadow Transit Egress of Europa
2012-Jan-11 08:53 Transit Egress of Europa
2012-Jan-11 09:39 Eclipse Reappearance of Io
2012-Jan-11 15:00 Transit of Great Red Spot
2012-Jan-11 16:54 Conjunction of Europa and Ganymede [124.5" W; 6.4" S]
2012-Jan-11 19:08 Eastern Elongation of Io, 123.4"
2012-Jan-11 19:33 Conjunction of Europa and Ganymede [151.7" W; 6.9" S]

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Credit: NASA