Astronomy news for the week starting Friday, November 10, 2000.

We begin the week with the near-full Moon, the phase passed on the afternoon of Saturday, November 11, shortly before moonrise in North America when it is moving between Aries and Taurus. That same night, the now-waning Moon will be seen up and to the right of Saturn, the Moon, Saturn and Jupiter lying on a curved line. The next night, that of Sunday the 12th, the Moon will fall between the two planets, and make a fine tight triangle with Jupiter and Taurus's Aldebaran. The brilliance of Jupiter (which the bright Moon cannot overcome) and the apparent closeness of the two will make the lunar motion easily visible, the Moon moving its own diameter in about an hour. Continuing the succession of days, on Tuesday the 14th, the Moon will pass perigee, when it is closest to the Earth.

The planetary list this week is topped by Mercury, as it will be at its greatest western elongation, that is, when it is as far west of the Sun as possible, the morning of Wednesday, the 15th. If you have never seen the little planet, this week gives a fine chance, one of the best of the year. Look to the southeast in growing twilight for a bright starlike point near the horizon. While quite bright, the planet is notoriously hard to see because of its proximity to the Sun, which makes it visible to the naked eye only in twilight and through the murk of the thick air near the horizon. Through the telescope, Mercury now takes on the appearance of a quarter-moon, as we see one-half in daylight, the other half in night. The poor visibility of Mercury makes it extremely difficult to see features on the planet, and most of what we know comes from radar studies and from the 1974-75 flybys of the Mariner 10 spacecraft, which showed the planet's ancient surface to be devastated by heavy cratering much like that of the Moon. Though the smallest planet (excepting odd Pluto), it has the distinction of being the densest and having the largest iron core relative to its size of any of the nine. And while admiring the association of the Moon with the giant planets and contemplating Mercury, do not forget brilliant Venus, easily seen now in the southwest after sundown.

The northern hemisphere is now in Cassiopeia season. From mid- northern latitudes, the famed "W" is nearly overhead around 9 PM. Opposite Polaris and the North Celestial Pole, the Big Dipper glides along the northern horizon. From above 41 degrees north latitude, the Dipper is circumpolar, never setting at all. If you have a clear northern horizon, take a look. The well-known "Moon illusion" artificially makes the rising full Moon look huge when on the horizon. Constellations suffer the same effect, the Dipper looking enormous as its parent constellation, Ursa Major, the Great Bear, walks beneath the pole.
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