Astronomy news for the week starting Friday, October 6, 2000.

It takes the Moon 29.5 days to run through its phases, the period the basis for our calendar month (which we stretch out to fit the year). Since a quarter of the lunar phase cycle is slightly longer than a week, we can have a full week with no lunar quarterings (new, first quarter, full, last quarter). Skylight's current week starts a day after first quarter and concludes the day before full. The entire week is therefore spent in the waxing gibbous phase, in which the sunrise line on the Moon slowly creeps across the visible lunar surface. (With a telescope you can see the mountains, really crater rims, at the sunrise line catching the first rays of sunlight). We also begin the week, on Friday the 6th, with the Moon at apogee, its most-distant point from Earth. As it moves against the constellations of the Zodiac, the Moon passes south of Neptune around midnight (in North America) the night of Friday the 6th, and south of Uranus about the same time the following night, both planets in Capricornus.

The week belongs not so much to the Moon, however, but to the planets. Venus, by far the brightest of all planets, is now becoming remarkably prominent to the west in evening twilight. If you are lucky, you might also spot Mercury down and to the right of Venus. The little planet comes into greatest eastern elongation relative to the Sun this week (when it is angularly farthest from the Sun), giving it the best evening visibility for this particular orbit. However, the planet remains elusive, as the western evening portion of the ecliptic (the apparent path of the Sun, which the planets closely follow) lies close to the horizon this time of year, and as a result, Mercury stays in bright twilight.

Later in the evening, Saturn, and brighter Jupiter, make their marks in the east, both well above the horizon by 10 PM. The pair are now wonderful showpieces in the early morning sky at dawn, both nearly overhead and set within the jewel-like stars of Taurus, the yellowish colors of the giant planets beautifully contrasting with Taurus's bright star Aldebaran. To the south at that time are the great icons of winter, Orion, with reddish Betelgeuse and blue- white Rigel, and down and to the left, the brightest star of the sky, Sirius in Canis Major. Early morning is a fine time to view such stars as the weather is still warm and many of the lights of town have been turned off, allowing the sky to be dark once again.

The evening is not without its charms, however, as by 10 PM the Great Square of Pegasus is high to the southeast, and the "W" of Cassiopeia is climbing the northeast. Look too to the lonely star Fomalhaut in Piscis Austrinus, the Southern Fish, as for most people in North America it glides above the southern horizon.
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