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The Shallow Sky

Planets in January 2002

Akkana Peck

I hope you got a good view of the lunar occultation of Saturn on December 27-28! If you're reading this before the event, disappearance is at 12:10 a.m., reappearance at 1:28. If you're reading this after the event and got clouded out, don't worry - you'll get another chance to see a Saturn occultation on Feb 20.

The first day of the new year begins with a Jupiter opposition. The giant planet is about as close to us as it ever gets, and is visible all night long. Near midnight it sits near the zenith, perfectly placed for detailed telescopic observing. We should get an excellent view of the great red spot (GRS), along with the wealth of activity that's been occurring in Jupiter's equatorial bands this year - I've heard reports of numerous barges (dark spots), light colored spots, and a large reddish spot on the opposite side of the planet from the GRS.

There isn't much in the way of multiple shadow transits this month. On the 30th, Callisto's shadow exits the planet at about the time Europa's enters, at about 6:30 p.m., and Europa's shadow proceeds to cross the planet's disk right on the edge of the GRS, with Europa itself preceding. On the 21st starting at nightfall, Io, Europa, and Callisto all dance closely together on one side of Jupiter for several hours (while poor Ganymede holds up the wall on the other side). Take a look, and see if you can tell the moons apart when they're all so close together. (Ganymede, much bigger than the other three, is usually easy to identify, but the other three moons can be tricky to tell apart, especially when they're all close to the planet so you can't use distance as an identifier. Hint: Io is often visibly redder than Europa or Callisto.) As always, you can use my Java Jupiter applet ( to predict moon, shadow, and GRS positions, if you don't have a planetarium program that shows this information.

While you're waiting for Jupiter to rise out of the muck, feast your eyes on Saturn, which is high enough for good viewing shortly after nightfall, and is still very close to us, only a month past its opposition. Its ring tilt is near maximum - you can follow the outer A ring all the way around the backside of the planet, and the shadow of the planet on the rings should be very nice. With the rings so open, see if you can see the northernmost parts of the globe through Cassini's division in the rings. Try high powers - Saturn is notoriously forgiving of high powers, and looks good in any telescope from small refractors all the way up to big reflectors. Naked eye observers continue to have a lovely view of bright Saturn making its way through the Hyades cluster in Taurus.

The early evening also offers us Mercury, low in the southwest during the first half of the month and showing a gibbous phase - it passes just over a degree away from Neptune (which is otherwise too to faint to be observable in the twilight) on the 9th - and Mars, shrinking in size but still bright enough and red enough to be noticeable. The dust storm which blocked our views during the Martian opposition seems to be fading, but the planet's small size will make it challenging to see any detail.

Venus, Uranus, Neptune, and Pluto are all too close to the sun to be easily observable during January (except on the 7th, when it may be fun to try finding Neptune by its proximity with Mercury).

Mail to: Akkana Peck
Copyright © 2002 San Jose Astronomical Association
Last updated: July 19, 2007

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