Magnificent Jupiter will be in longitudinal opposition to the Sun on 2008 JUL 09 at 07:39 UT. Near that date it will be rising around sunset, transiting the meridian around local midnight and setting around sunrise. Those events occur about four minutes earlier each evening. Jupiter’s declination at opposition will be S 22.5°, meaning it still will be riding relatively low above the southern horizon for northern hemisphere observers. Its meridian transit altitude will be 67.5° minus your northern latitude.

Jupiter’s closest approach to Earth for this apparition will occur on 2008 JUL 10 at 4.1610 AU. Its apparent equatorial diameter will be 47.3 arcseconds with polar diameter at 44.2 arcseconds. Its stellar magnitude will be -2.7.

The apparent tilt of Jupiter’s equatorial plane will be -1.5° at opposition. That will reach 0° on 2009 APR 16. The apparent tilt oscillates with a major component equal to Jupiter’s approximately 12-year orbital period and a minor component contributed by Earth’s annual motion. It’s not an actual wobbling, but a change in our viewing perspective. The Galilean satellites all lie in planes close to Jupiter’s equatorial plane.

With the decreasing apparent tilt of the orbital plane of the Galilean satellites, #4 Callisto can once again be involved in transits, occultations, eclipses and shadow transits. The other three participate in all of these events each time they orbit Jupiter. But Callisto only does so during periods that last about three years in alternation with approximately three-year periods in which it appears to pass north or south of Jupiter at each conjunction.

The decreasing tilt means more of the satellite events will be occurring during this year’s apparition of Jupiter compared to recent years. Quadruple shadow transits are impossible due to a commensurability among the orbital periods of the inner three Galilean satellites. Triple shadow transits are only possible when #4 Callisto participates. However, this will never happen during the current series of Callisto shadow transits. The next triple shadow transit will occur in 2013. But numerous dual shadow transits will continue happening during the current apparition. The next such event will occur on 2008 AUG 05 during the pre-dawn hours for North Americans and will involve #1 Io and #4 Callisto.

Mutual passages among the Galilean satellites now appear closer than they have for several years. My calculations indicate that mutual occultations, transits and shadow transits/eclipses among the Galilean satellites will commence next year on 2009 MAR 27 and end on 2010 JAN 08. Immediately prior to and during that time period I will provide detailed predictions of the events.

On my website is a graphic illustrating the apparent retrograde loop of Jupiter as it zigzags against the background stars between now and November. To see it, click: http://www.curtrenz.com/astronomical.html

Photos and descriptions of Jupiter and its satellites during the current apparition would be welcome additions to this thread.

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Curt Renz - "Centaur"
For monthly astronomical calendar visit:
www.CurtRenz.com/astronomical.html

Here is Jupiter, imaged last night: