Astronomy news for the week starting Friday, January 19, 2001.

This week holds the new Moon, passed the morning of Wednesday, the 24th. Six hours later, it passes apogee, when it is farthest from the Earth. Before that date you can see the earthlit waning crescent in the morning hours to the east before sunrise, and afterward the reversed waxing crescent in the west after sunset. The Moon will be technically visible in western twilight the night of Thursday, the 25th, nearly in conjunction with (and below) the planet Mercury, but both will be quite difficult to see. By the night of Friday, the 26th, however, the slim lunar crescent (now well up and to the left of Mercury) will be quite visible. Mercury's visibility will improve until early next week, when it reaches greatest eastern elongation from the Sun.

Earlier in the week, on Monday the 22nd, Mercury passes close conjunction with Uranus, a quite-invisible event. At the end of the week (on Thursday the 25th), Uranus's near-twin, more-distant Neptune, finally passes conjunction with the Sun to become a morning object. Uranus will follow in early February. Though Mercury will be, as usual, hard to find, Venus will not, as it continues to blaze away in the southwestern evening sky.

In a highly unusual coincidence, both Jupiter and Saturn cease their westerly retrograde motions not only the same day (Thursday the 25th), but within about an hour of each other. It would be difficult to figure how often this happens without running actual orbital calculations, but it must be once in hundreds, if not thousands, of years. Odder still, Jupiter ceases retrograde first even though it is the more-easterly planet (ordinarily, the more- westerly ones finish first), a result of Jupiter's being closer to us than Saturn (4.4 as opposed to 8.6 astronomical units, the AU the average distance between the Earth and the Sun). Both planets will thereafter begin to move in their normal easterly direction against the background stars (for now, of Taurus), Jupiter pulling away from the ringed planet as it heads for the next constellation of the zodiac, Cancer.

Taurus (Jupiter and Saturn's temporary home) is at its best in the early evening around 8 PM. Look for the vee-shaped Bull's head made by the Hyades cluster, the Seven Sisters (Pleiades) up and to the right. Aldebaran, the Bull's orange eye, is only situated in front of the Hyades and is not actually a part of it. Taurus is one of the few constellations that link to another, the northern horn (which extends northeast of Aldebaran) tied to bright Auriga, the Charioteer, which with bright Capella, stands above Orion. The other linking constellations are northern autumn's Andromeda with Pegasus and summer's Ophiuchus with Serpens.
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