September 2000

by Steve Stefanik

September is the month of the autumnal equinox and the Harvest Moon, sure signs of Fall.

This year the first day of Fall occurs on the 22nd at 1:27 EDT when the sun crosses the celestial equator and begins its slow migration to the south. The apparent result is a decline in the sun’s altitude in the sky and a noticeable decrease in daylight hours. What may not be as apparent is the changing position of the rising and setting sun with each passing day until the sun reaches its most southerly point on the horizons on December 21 when the sun appears to stop moving south on the day of the Winter Solstice (sun stands still).

Speaking of standing still, two planets return to the late evening sky this month. Jupiter and Saturn rise in the east with the constellation Taurus "the bull". Saturn comes into view first. Look for this 0 magnitude pale orange orb just above the tiny star cluster the Pleiades. Jupiter rises about half an hour later. You won’t miss its -2.6 magnitude brilliance. The pair appear as darts with hundreds of stars of the Hyades star cluster in the background as the "dartboard" with the red-orange first magnitude star Aldebaran near the center which is "the bull’s eye". On September 12th, Saturn stops it eastward movement and appears to stand still on that night before retrograding (moving backward) westward. Jupiter stands still on the night of the 29th. Because of this the two planets spend the next several months in the constellation Taurus keeping pace with its normal westward motion. As a result they will provide us with numerous nights to observe them throughout the dark Fall and Winter nights ahead.

The planets Uranus, Neptune, and Pluto are high in the southern sky during the evening amidst the stars of the constellations Ophiuchus and Capricornus but you’ll need a telescope and patience to spot them.

The only other planets to possibly catch a glimpse of are Venus, Mercury, and Mars.

Venus and Mercury are low in the west-southwest only a few degrees above the horizon. They are near the bright first magnitude star Spica in the constellation Virgo which is setting in September. You could try to spot them by scanning the western horizon with binoculars after the sun goes down for about an hour at best.

You’ll have to be up before sunrise to catch a glimpse of Mars. It rises with the stars of the constellation Leo "the lion". On the morning of the 16th see if you can spot the relatively dim +1.8 magnitude "red planet" near Leo’s brightest first magnitude blue-white star Regulus.