Astronomy news for the week starting Friday, September 24, 1999.

Welcome to northern hemisphere autumn, begun last Thursday the 23rd as the Sun passed the autumnal equinox in Virgo and crossed the celestial equator into the southern hemisphere. For the next six months, sunrises and sunsets will be to the south of due east and west.

This is not only the first full week of autumn, but also the week of the full Moon, the phase reached the night of Friday the 24th, about the time of moonset the morning of the 25th (and almost exactly two full days past the beginning of fall). With the Sun only two degrees to the east of the autumnal equinox, this full Moon will be very close to the vernal equinox in Pisces, the rising Moon on Friday the 24th just a bit to the west of it. This full Moon, the "harvest Moon," is perhaps the most famed of them all. At this time of year, the ecliptic, the solar path that the Moon closely follows, lies flat to the eastern horizon at the time of sunset. As a result, the waning gibbous Moon just past full continues to rise quite early, flooding the countryside with bright moonlight.

The sky is now quite filled with planets. In the early evening, Mars is still visible low in the southwest above and to the left of the bright star Antares. Then it is just a short wait until 9 PM or so when brilliant Jupiter lofts itself above the trees and buildings to the east, followed about an hour later by bright Saturn, the two quite unmistakable as they climb the evening sky. Watch as the Moon moves to the southwest of Jupiter the night of Sunday the 26th and to the southwest of Saturn the night of Monday the 27th. Finally, in early dawn, with Jupiter and Saturn moved into the western sky, brilliant Venus dominates the east, the planet reaching greatest brilliancy in this turn of its orbit on Sunday the 26th, the planet so bright it throws shadows and is quite visible in a clear daytime sky. Of the bright planets, only little Mercury is left out, too low in the west at sunset to be visible.

As the Moon moves out of the way, we will become more aware of the brilliance of the stars that take us from summer to autumn. In early evening in mid-latitudes, the Summer Triangle of Vega, Deneb, and Altair lie nearly overhead, the Milky Way streaming through Cygnus and Aquila on its way to the center of the Galaxy in Sagittarius, while to the east the Great Square of Pegasus rises like a giant diamond foretelling the crackle of the fall days to come.
Valid HTML 4.0!