Astronomy news for the week starting Friday, October 22, 1999.

All sorts of things happen at about the same time this week. The Moon passes its full phase on Sunday the 24th in the middle of the afternoon in North America, therefore rising just past full and just after sunset among the faint stars of southern Aries. The day before, on Saturday the 23rd, Jupiter comes into opposition with the Sun, rising at sunset, setting at sunrise, and crossing the celestial meridian to the south at local midnight (1 AM daylight time). Since the full Moon is also opposite the Sun, Jupiter and the full Moon will rise close together the night of Sunday the 24th, Jupiter a bit in advance and to the northwest of our satellite. Saturn, only 15 degrees to the east of Jupiter, rises about an hour later. Since the Moon moves about 13 degrees per day against the stellar background, it will rise to the southeast of Saturn the night of Monday the 25th. Later in the week, the night of Tuesday the 26th, the Moon will pass to the north of Aldebaran in Taurus.

Not only is Jupiter in opposition to the Sun, but little Mercury reaches greatest eastern elongation, when it is as far to the east of the Sun as it can get, also on Sunday the 24th. Unfortunately, the evening ecliptic, to which the planets cling, lies quite flat to the horizon, and Mercury is rather lost in western twilight glare. The day before, on Saturday the 23rd, Uranus, just to the east of Neptune, ceases its westerly motion against the stars of Capricornus, and begins once again its normal easterly movement as it slowly orbits the Sun.

Attention drawn to the rising full Moon makes observers note the apparent huge size of the lunar disk. The Moon in fact is no larger when on the horizon than it is when high in the sky (one- half a degree). Its apparent large size is only an optical (and well-studied) illusion. In fact the Moon is a bit angularly larger than usual this week, as it passes perigee, its closest point to the Earth, on Tuesday, the 26th, but that effect is actually not sensible to the human eye.

Finally, the week is also host to one of the year's better meteor showers, the Orionids, which peak on Thursday, the 21st, the meteors best seen in the early morning hours after the rising of Orion. Unfortunately, the bright waning gibbous Moon will blot out the fainter ones. Nevertheless, a few bright meteors, the debris of Halley's Comet, may still be observed competing with the brilliant morning glow of Venus, seen to the east before dawn.
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