by Geoff Chester, USNO Public Affairs | 24 September 2024 The Lights of Washington, DC, as seen from Skyline Drive, August, 2023 imaged from Thoroughfare Mountain overlook, 75 miles west of the city. The Moon wanes in the early morning sky this week as she passes through the rising winter constellations. New Moon falls on October 2nd at 2:49 pm Eastern Daylight Time. If you’re up well before the Sun, look for Luna just over one degree from the star Pollux, one of the “Twin Stars” of Gemini. The September observing campaign for the Globe at Night citizen science program begins on the 24th and runs through October 3rd. This is a great time to familiarize yourself with the stars and raise awareness of the effects of light pollution on the environment. For the past 16 years the program has amassed more than 200,000 observations by night sky enthusiasts around the world, charting the growth of unnecessary outdoor lighting that is gradually stealing our view of the universe. The target constellation for this month is Cygnus, the Swan, which seems to “fly” southward through the stars of the Summer Triangle, which lies overhead as evening twilight gives way to night. The Swan’s brightest star, Deneb, is the northernmost star in the Triangle asterism, and in Greek mythology marked the Swan’s tail. From a dark location it is quite easy to trace a stick-figure swan from Deneb to the star Albireo, which lies in the middle of the Triangle. Urban dwellers may just be able to see a large cross-shaped asterism filling in the northeast section of the Triangle. Once you have found Cygnus, go to the Globe at Night’s web app page to record your observation. Light pollution has wide-ranging effects that interfere with our circadian rhythms, bird migration, animal behavior, and climate change. It also deprives us of the cultural links to a time when people turned to the stars to populate their myths and legends. It has been estimated that some 85 percent of the people on Earth have never seen the Milky Way, and most of us who live in and near major urban areas can no longer make out any of the constellations except the brightest ones. Cygnus holds an abundance of interesting objects for owners of small to modest telescopes. In addition to the beautiful blue-gold double star Albireo, there are several other interesting pairs of stars to view. One of these, 61 Cygni, is located about eight degrees southeast of Deneb. While it is a relatively faint star, it is steeped in astronomical history. In 1792 the Italian astronomer Giuseppe Piazzi noticed that it had moved from the position recorded 40 years earlier by the English astronomer James Bradley. Piazzi charted its motion, and in a paper published in 1804 speculated that it must be a nearby system. He dubbed it the “Flying Star”. In 1838 the German astronomer Friedrich Bessel made the first measurement of stellar parallax using 61 Cygni, and determined its distance as 10.4 light years, the first reliable measurement of the distance to a star other than the Sun. The modern value is 11.36 light years, and the Flying Star is one of the few stars whose motion through space can be measured with amateur telescopes. In addition, it is a very attractive pair of yellow-tinted stars that can be easily split in a small telescope. The bright planet Venus is now beginning to climb out of the glow of evening twilight. If you have a god view of the western horizon you should be able to spot her shortly after sunset. By the beginning of October the dazzling planet sets about an hour and twenty minutes after Old Sol. Saturn is the brightest object that you will see in the southeastern sky as evening astronomical twilight ends. His cheery yellow glow forms the upper apex of a triangle with the first magnitude star Fomalhaut, located about halfway between Saturn and the horizon at 10:30 pm, and the second-magnitude star Diphda, the brightest star in Cetus, the Whale. Bright Jupiter rises at around 10:30 pm as we swing into October, perched between the two stars that mark the “horns” of Taurus, the Bull. The giant planet will spend the upcoming months in the company of the bright stars of the Great Winter Circle, helping them to brighten the long nights of the upcoming solstice season. Ruddy Mars now rises shortly after midnight, but he is still best seen during the early morning hours. His distinctive red tint shines among the stars of Gemini. Look for the red planet below the waning crescent Moon on the morning of the 25th. Between them will be the orange-tinted third-magnitude star Mebsuta.