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March 13: Look into the eyes of the Owl
A transit of Io and its shadow occurs early this morning, after which Io reaches the western extent of its orbit and comes back around, passing behind Jupiter in an occultation visible late tonight.
First up is the transit, which begins at 2:52 A.M. EDT this morning, with Jupiter — currently located in Gemini — quickly sinking in the west for the eastern half of the U.S. Io is moving from east to west, and by the time its shadow joins in at 2:00 A.M. MDT, the planet has set for observers in the Eastern time zone and is very low for those in the Central time zone. As its shadow creeps inward from the eastern limb, Io sits in the middle of the disk, moving quickly toward the western limb. Io’s transit ends shortly after 2 A.M. PDT, with its shadow now approaching the middle of Jupiter’s visible disk.
This evening, Io has come back around and is approaching the western limb as darkness falls. It finally slips behind the disk late tonight, around 12:10 A.M. EDT (now on the 15th in the Eastern time zone only). It won’t reappear until 2:40 A.M. CDT on the 15th, with Jupiter too low for East Coast observers to catch it. That reappearance also occurs some 20” east of the planet’s eastern limb, as Io has traveled not only behind the planet but also through its long, dark shadow, which extends east of the planet in space, showing off the geometry of the Earth, Sun, and Jupiter to give us this view.
Sunrise: 7:13 A.M.
Sunset: 7:06 P.M.
Moonrise: 5:02 A.M.
Moonset: 2:28 P.M.
Moon Phase: Waning crescent (17%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
