Astronomy news for the week starting Friday, September 21, 2001.

Our Moon passes its first quarter early in the week, on Monday the 24th, brightening as it heads toward its full phase next week. That same night it will make an especially good pass at Mars (now in Sagittarius), when in the early evening it will be only 2 degrees directly to the north of the red planet. The configuration will provide a fine chance to see the lunar motion, as the Moon moves through its own diameter in about an hour. The night of Wednesday the 26th, the Moon will visit Neptune, the night of Thursday the 27th Uranus, both planets within the confines of Capricornus.

The morning sky remains glorious, with Saturn, brighter Jupiter, and yet-brighter Venus all strung out on a line from high in the sky toward the eastern horizon, the three planets roughly defining the ecliptic -- the plane of the Solar System -- rather like a dotted line. Saturn (still in Taurus), now rising around 10:30 Daylight Time, passes a watershed during this round of evening visibility when it begins retrograde -- backward -- motion the night of Wednesday the 26th, as the Earth prepares to pass in between the Sun and the ringed planet. Jupiter (beautifully set amidst the stars of Gemini), rising around 12:30 AM daylight time, prepares to move into evening as well.

It is planet Earth, however, that takes center stage, when it crosses into the sky's southern hemisphere at the autumnal equinox in Virgo at 6:04 PM Central Daylight Time (7:04 Eastern, 4:04 Pacific) on Saturday the 22nd, and astronomical autumn begins in the northern hemisphere (and spring in the southern). On that day the Sun will rise very close to due east and set close to due west all over the Earth except at the poles. At the north pole, the Sun will officially set (though because of its finite diameter and atmospheric refraction it will still be visible); at the south pole scientific stations, the Sun will officially rise and be up for the next six months. At the Earth's equator, the Sun will pass through the zenith, the point overhead.

As we move into fall, the summer constellations begin to make their exit to the west, Scorpius appearing low in the southwest, giant Ophiuchus, the Serpent Bearer, standing above the scorpion more to the west. To the east look for the Great Square of Pegasus, which has already risen by nightfall. To the left of the Great Square, runs the graceful string of stars that makes most of Andromeda, and coming up in the northeast is the "W" of Cassiopeia. Still, the memory of summer lingers through the Summer Triangle of Vega, Deneb, and Altair, which in early evening is nearly overhead in mid-northern latitudes.
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