Skywatch Line for Friday, September 8, through Sunday, September 10, 2023

This is Dudley Observatory’s Skywatch Line for Friday, September 8, through Sunday, September 10, written by Sam Salem.

On Friday, Sun rises at 6:27am and sets at 7:18pm; Moon sets at 4:18pm. The waning crescent Moon rises around 3:00am on Sunday morning under stars Castor and Pollux, in the constellation of Gemini. By early dawn they’re a vertical lineup high in the east.

Venus, at magnitude –4.6, is emerging low in the dawn due east. It gets higher and easier every day. Low magnification shows that Venus is a thin crescent. The crescent will get thicker and smaller in the coming weeks as it climbs higher in the dawn.

Jupiter, at magnitude –2.6 in the constellation of Aries, rises about an hour after dark. Watch for it to come up low in the east-northeast. It shines highest in the hours before dawn.

Saturn, at magnitude +0.4 in dim constellation of Aquarius, sits low in the southeast in twilight. It’s at a good height for telescopic observing by 11:00pm, by which time Fomalhaut is twinkling two fists below it. Saturn is highest in the south around midnight.

The Great Square of Pegasus is high in the east after dark, balancing on one corner. From the Great Square’s left corner extends a big line of three 2nd-magnitude stars, running to the lower left, that mark the head, backbone, and leg of the constellation Andromeda. Upper left from the foot of this line you’ll find W-shaped Cassiopeia tilting up.

Two of the best-known deep-sky objects are in high view by 10:00PM. The first one is the Double Cluster in Perseus, just below Cassiopeia. The second is the Great Andromeda Galaxy, M31. They’re about 22 degrees apart. They’re both cataloged as 4th magnitude but to the naked eye they look rather different. They’re below Cassiopeia and farther to Cassiopeia’s right, respectively.

Summer is ending for us in the Northern Hemisphere. A major sign of winter looms large now in the predawn sky. The waning crescent Moon can guide your eye to this large lasso of stars, the Winter Circle, on Friday and Saturday mornings. The Moon will be passing through the Circle on those mornings. The Winter Circle, also called the Winter Hexagon, is an asterism, or recognizable pattern of stars. It consists of six stars in six different constellations. They are all associated with the winter sky in the Northern Hemisphere. The Hexagon vertices are at Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius. Find the star Rigel in the constellation of Orion, then start moving around the circle clockwise.