SKYLIGHTS

Astronomy news for the week starting Friday, September 28, 2001.

Welcome to the first full week of autumn (if you are in the north) or spring (if in say Chile, Argentina, or Australia), the seasons reversed between hemispheres. The lunar phases of course are not, as everyone in the world will see the Moon pass through its full phase on Tuesday, October 2. In the Americas, full phase actually occurs shortly after moonset, so the night of Monday October 1 the Moon will be just before full and will rise before sunset, the night of Tuesday the 2nd it will be just after full phase and will rise just after sunset within the Earth's rising shadow. Full moonrise is often spectacular, the Moon looking larger than normal, the effect purely an optical illusion. Because of the low tilt of the eastern portion of the ecliptic against the horizon, the nightly delay in moonrise is short and the evening seems flooded for several nights with near-full-moonlight. Though the October full Moon is traditionally called the "Hunter's Moon," this year it is closer to the fall equinox than was the September full Moon, and more fits the concept of the "Harvest Moon."

Because the Sun has just passed the autumnal equinox in Virgo, this full Moon will be just past the vernal equinox in Pisces, though the dimness of the constellation will render it quite invisible. In between fall and spring lies winter, so between the autumnal and vernal equinoxes lies the winter solstice in Sagittarius, which is right on the meridian to the south at sunset. Embracing bright reddish Mars, Sagittarius will thus be just to the west of south as twilight ends. Look just below Mars to see Sagittarius's five-star Little Milk Dipper, the red planet passing just north of bright Nunki (Sigma Sagittarii) the night of Sunday, September 30.

In the evening sky, among the bright planet Mars is still quite alone. Watch, however, for the rising of Saturn around 10 PM Daylight Time (the ringed planet to the east of Aldebaran in Taurus). Two hours later, bright Jupiter, in Gemini, crosses the evening divide, rising now about midnight Daylight Time. In the morning hours, Venus, though getting closer to the horizon, still gleams brilliantly in growing dawn.

At 9 PM, Deneb, in Cygnus, flies is high in northern-hemisphere skies near the zenith. Look to the south to find one of the sky's more exquisite constellations, Delphinus, the Dolphin, appearing something like a parallelogram that makes a hand with a finger pointing southward. Just west and a bit north lies Sagitta, the Arrow, and north of that very dim Vulpecula, the Fox, a challenge even on a moonless night (which these are not).