This is Dudley Observatory’s Skywatch Line for Friday, August 28, through Sunday, August 30, written by Sam Salem.
On Friday, Sun rises at 6:16am and sets at 7:36pm; Moon sets at 1:17am and rises at 5:11pm. On Friday evening, the waxing gibbous Moon will sit just two finger widths below Jupiter with Saturn to their left. Both objects will fit within the field of view of binoculars. During the night, the diurnal rotation of the sky will move the Moon to Jupiter’s left by the time they set, at about 2:30am. On Saturday evening, the Moon will hop east to sit a palm’s width to the lower left of Saturn. During the night, the diurnal rotation of the sky will lift the Moon higher than Saturn.
On Sunday night, the terminator on the waxing gibbous Moon will fall just west of Sinus Iridum, the Bay of Rainbows. Sinus Iridum is almost craterless but hosts a set of northeast-oriented “wrinkle ridges” that are revealed at this lunar phase. The circular 155-mile diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its east, forming a rounded “handle-shape” on the western edge of that mare. The “Golden Handle” effect is produced by way the slanted sunlight brightly illuminates the eastern side of the prominent Montes Jura mountain range surrounding the bay on the north and west. And by a pair of protruding promontories named Heraclides and Laplace to the south and north. Use a lunar map to help you locate these Moon features.
Venus beams in front of the great big lasso of stars known as the Winter Circle. For the next several days, Venus shines at the eastern border of the Winter Circle, midway between the Procyon, the Little Dog star, and the Gemini stars, Castor and Pollux. The Winter Circle dwarfs constellation Orion, the Hunter, which only makes up the southwest, or lower right portion of the Winter Circle. If you are acquainted with Orion, this constellation presents a great jumping off place for circumnavigating this Winter circle of stars. From Rigel in Orion, go to Aldebaran in Taurus, to Capella in Auriga, to Castor and Pollux in Gemini, to Procyon in Canis Minor, to Sirius in Canis Major. In late August, the Winter Circle returns to the morning sky. But we still won’t see the Winter Circle in the evening sky for months to come.
On Friday, the dwarf planet, formerly asteroid, Ceres will reach opposition, its closest approach to Earth for the year. On the nights around opposition, Ceres will shine with a peak magnitude of 7.2, well within reach of binoculars and backyard telescopes. Ceres will be situated only palm’s width above the bright naked-eye star Fomalhaut, in constellation Piscis Austrinus. Both objects will easily fit within the field of view of binoculars. Ceres will already be climbing the southeastern sky after dusk. It will reach its highest elevation, and peak visibility, over the southern horizon after 1am.
The Great Square of Pegasus is a great jumping-off point for finding Andromeda galaxy, or Messier 31. The Great Square of Pegasus sparkles over the eastern horizon at about 9:00pm in late August and early September. Locate the Great Square of Pegasus in your eastern sky. You’ll see the constellation Andromeda as two streamers of stars jutting up from the uppermost Great Square star. The two streamers mimic the shape of a cornucopia or a bugle. Go to the second star upward on each streamer, Mirach and Mu Andromedae. Draw an imaginary line from Mirach through Mu, going twice the Mirach/Mu distance, you locate the Andromeda galaxy. On a dark night, the Andromeda galaxy looks like a faint, blurry patch of light.