Astronomy news for the week starting Friday, August 27, 1999.

The Moon is in its waning gibbous phase this week, a time when most of the visible lunar disk is in sunlight. Third quarter, which begins the waning crescent portion of the lunar journey, takes place on Thursday, September 2. At almost the same time, the Moon passes its perigee, when it is closest to the Earth. As it makes its journey against the stars of Pisces and Aries, it passes south of Jupiter the night of Monday the 30th, then south of Saturn the night the 31st.

Mars, moving rapidly now among the stars of far eastern Libra (up and to the right of the trio of stars than make the head of Scorpius) still dominates the early planetary evening sky, glowing redly in the southwest. But it does not dominate long, as brilliant Jupiter encroaches on the evening, rising in the east now around 10 PM, followed within the hour by Saturn. Jupiter, the planetary system's giant, 11 times the size of Earth, entered retrograde, or westerly motion, last week, and now it is Saturn's turn, as it stops travelling easterly and begins its backward trek on Monday, August 30 (caused by the Earth beginning to swing between it and the Sun). Though over the long haul Jupiter is getting closer to Saturn, while the two planets are in retrograde Jupiter will temporarily pull away.

As the Moon dims and clears out of the way, the night sky is again revealed. One of the best times of the year for viewing, rivalled only by the depth of winter, which contains Orion's family, late August and early September feature the summer Milky Way. Hard to see from town, in a dark sky the Milky Way brilliantly streams from Cygnus (nearly overhead in mid-northern latitudes) toward the south through Aquila and into Sagittarius where it broadens around the center of the Galaxy. In 1610 Galileo announced that this broad band of light consisted of countless stars. We now know it be the combined light of the disk of our 200-billion-star Galaxy, in which we live. While admiring the night, don't forget the day. The third quarter Moon appears high to the south at sunrise and is visible during morning hours as it moves to the west. The Sun is also moving quickly to the south as it approaches the Autumnal Equinox at a rate of a third of a degree per day, resulting in rapid daily changes in the time of sunset and sunrise.
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