Skywatch Line for Friday, August 25, through Sunday, August 27, 2023

This is Dudley Observatory’s Skywatch Line for Friday, August 25, through Sunday, August 27, written by Sam Salem.

On Friday, Sun rises at 6:12am and sets at 7:42pm; Moon rises at 3:50pm.

On Sunday, the waxing gibbous Moon shines in the south after dark. High above it, by three or four fists at arm’s length, spot 1st-magnitude Altair with its little sidekick, 3rd-magnitude Tarazed, or Gamma Aquilae, about a finger-width above it. Much closer to the right of the Moon is the Sagittarius Teapot. Its four-star handle is the part closest to the Moon, less than a fist at arm’s length. About a fist right of the handle, and a bit lower, is the Teapot’s spout. Use binoculars to help through the moonlight.

Venus, about magnitude –4.3, emerges very low in brightening dawn. Look for it just above the horizon due east starting about 20 minutes before sunrise. Binoculars will help. Venus gets higher and less difficult every day. Low magnification will show that, as Venus emerges from inferior conjunction, it’s again a very thin crescent. The crescent will get thicker and smaller in the weeks to come as it shines higher in the dawn.

Jupiter, at magnitude –2.5 in the constellation of Aries, rises around 11 p.m. Watch for it to come up low in the east-northeast. By the beginning of dawn, Jupiter shines very high in the south.

Saturn, at magnitude +0.5 in dim constellation of Aquarius, rises in bright twilight. In late twilight you’ll find Saturn glowing as the brightest thing low in the east-southeast. Saturn is at opposition on Sunday at 4am. In a telescope, notice that Saturn’s rings are distinctly brighter, compared to Saturn’s globe, than you usually see them. This is the Seeliger effect, caused by the solid ring particles backscattering sunlight to us when the Sun is almost directly behind us. The dusty surfaces of the Moon and Mars also display this “opposition effect,” but Saturn’s clouds do not. In the case of Saturn, the effect is named for Hugo von Seeliger, who studied it in detail and published his findings in 1887. The brightening begins several days before Saturn’s opposition, is strongest right around that date, and fades for several days after. Saturn is at a good height for telescopic observing by 11pm, by which time Fomalhaut is twinkling two fists below it. Saturn is at its highest in the south around 1am.

Andromeda Galaxy is the great spiral galaxy next door to the Milky Way, and the most distant object you can see with your eye alone. It’s best seen in the evening at this time of year, in a dark moonless night. Bright moonlight or city lights can overwhelm the faint glow of the Andromeda Galaxy. Find the galaxy by star-hopping from the constellation of Cassiopeia the Queen, a very noticeable M- or W-shaped pattern on the sky’s dome. You can also find the Andromeda Galaxy by star-hopping from the star Alpheratz in the Great Square of Pegasus. In a dark sky, look northward for the M- or W-shaped constellation Cassiopeia the Queen. Next, locate the star Schedar in Cassiopeia. It’s the constellation’s brightest star, and it points to the Andromeda Galaxy. Here’s another way to find the Andromeda Galaxy. The constellation constellation Andromeda can be seen as 2 streams of stars extending from one side of the Great Square of Pegasus.

Locate the star Alpheratz. It joins Pegasus to Andromeda. Now, notice the star Mirach, followed by Mu Andromedae. An imaginary line drawn through Mirach to Mu points to the Andromeda Galaxy.