Skywatch Line for Wednesday and Thursday, July 5 and 6, 2023

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, July 5 and 6, written by Alan French.

The Sun rises at 5:23 A.M. on Wednesday and sets at 8:37 P.M. On Thursday it rises at 5:24 and sets at 8:36. This Thursday has just under 5 ½ minutes less daylight than last Thursday. We are losing daylight at an increasing rate as the Sun moves farther south.

The Moon was full Monday morning and is now moving toward last quarter. A waning gibbous Moon rises late, leaving the early evening sky moonless and dark. Moonrise on Wednesday night is at 10:55 and it rises at 11:24 Wednesday. On Wednesday it is 89% full when it rises and on Thursday moonrise reveals an 81% sunlit Moon. It will reach last quarter on Sunday evening.

Brilliant Venus continues to grace the western sky as darkness falls. At 9:15 it is 14 degrees above the horizon. Through a telescope it now appears just over 36 arcseconds across and as a 28% illuminated crescent. Traveling on its faster, inner orbit it will continue to grow larger and we’ll continue to see less of its sunlit face as it catches up with our Earth.

Fainter Mars is now just under 4 degrees away from Venus, located at about the 11 o’clock position. Regulus, the brightest star in Leo, the Lion, is 6 ½ degrees away at about the 10 o’clock position from Venus.

High in the east at 10:30 P.M., 66 degrees above the horizon, you’ll find the fifth brightest star in the night sky, Vega. Vega is the brightest star in the constellation Lyra, the Lyre. Like most of the bright stars in the night sky, it is bright because it is one of our closer stellar neighbors, lying just 25 light years away. The light you see, travelling at 186,000 miles per second, took 25 years to reach you.

Lyra is a small, easily recognized constellation. Looking at Vega high in the east around 10:30, you’ll spot a single star to its lower left, just under two degrees away. (The tip of your little finger, held at arm’s length, spans 1 degree.) To the lower right, you’ll see a parallelogram of stars, the closest two degrees away. The longest side of the parallelogram spans 4 ½ degrees. (Held together at arm’s length, your three longest fingers span 5 degrees.)

The constellations vary in size. The largest three, Hydra, the Water Snake, Virgo, the Maiden, and Ursa Major, the Great Bear, each take up a little over three percent of the sky. In terms of size, Lyra is small, taking up just 0.69% of the sky and ranks as 52nd in size of the 88 constellations.

The smallest three constellations are Sagitta, the Arrow, Equuleus, the Little Horse, and Crux, the Cross. Each takes up less than 0.2% of the sky. Crux is too far south to be spotted from our area.