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Clouds and Lake Erie

Photo of the Week.. Planet Earth: Ranks of clouds line up toward Lake Erie at the top.

Astronomy news for the week starting Friday, January 18, 2002.

We begin the week with the Moon at its farthest from the Earth, at apogee, as it heads toward its first quarter, which it will reach on Monday, January 21st, roughly the time it rises in North America. The night of Friday, the 18th, watch as the Moon passes to the south of Mars. Set below the Circlet of Pisces, the red planet is practically on the ecliptic, the apparent path of the Sun. The lunar orbit is rather tilted, however, and on the 18th, the Moon will be about as far south of the ecliptic as it can get, and hence will not come close to covering, or occulting, Mars.

As the Moon orbits, it will approach the ecliptic path, and as it goes over the top to the north in Taurus and Gemini, will in fact occult first Saturn and then Jupiter on Thursday the 24th and Saturday the 26th respectively. The events happen in the daytime in the Americas, however. As a result, the Moon will be to the west of Saturn the night of Wednesday, the 23rd, and to the east of it the following evening. Saturn is now just to the east of the Hyades in Taurus. The juxtaposition of the growing gibbous Moon, the Hyades with Aldebaran, Saturn, and the Pleiades just to the north, will make an especially grand sight, one not to be missed. And don't forget Jupiter, not far to the east. Both giant planets are well up in the east by sunset. Saturn crosses the meridian to the south around 8:30 PM, while Jupiter follows two hours later. If you have access to a telescope, be sure to take a look at both of them. Saturn's rings, made of countless small ice-coated rocks, are wide open and an easy sight, while on Jupiter you can trace out dusky cloud belts formed within the planet's ammonia clouds. Jupiter's four bright moons -- in order outward Io, Europa, Ganymede (a bit bigger than Mercury, the largest moon in the Solar System), and Callisto -- are visible even in binoculars. In even the smallest telescope, Saturn's big moon Titan will pop out at you. Titan is covered with a thick atmosphere, and is suspected of having an ocean made of methane and ethane. We will know better when the Cassini probe gets there in 2004.

The sight on Wednesday and Thursday nights gets even better when you take into account the surrounding brilliant winter constellations. Down and to the left of Saturn and the Moon find wonderful Orion, the giant hunter of ancient Greek mythology. Above the Moon will be Auriga, the Charioteer, with bright Capella and the three-star triangle called "the Kids." To the left of Orion bark his two "hunting dogs," Canis Major (the larger) with brilliant Sirius below, Canis Minor, with Procyon, above. Taken together, there are few better celestial sights.
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