by Geoff Chester, USNO Public Affairs | 20 August 2024 The Milky Way, imaged from Stellafane, Breezy Hill, Vermont, 2023 August 18 with a Canon EOS Rebel SL2 DSLR and an Omegon Mini-Track LX-2 mechanical star tracker. Composite of two stacked exposures The Moon wanes as she climbs through autumn’s rising constellations, starting the week off with a very close conjunction with the planet Saturn. The two objects will be just half a degree apart when they rise together shortly before 9:00 pm local time on the 20th. By the end of the week, she joins the rising winter constellations in the pre-dawn hours. Last Quarter occurs on the 26th at 5:26 am Eastern Daylight Time. Look for Luna just to the southeast of the Pleiades star cluster on the morning of the 26th. On the following morning she passes five degrees north of bright Jupiter. The pair form a photogenic triangle with the bright stars of Taurus as a background. August is the month when most of us really begin to notice the change in the length of the day. This week we are just one month away from the autumnal equinox, and we are entering the period when each passing day loses over 2.5 minutes of daylight over the previous one. Here in Washington the time between sunrise and sunset is now over an hour less than it was just one month ago. While a few minutes doesn’t seem like much on a day-to-day basis, the effect becomes much more pronounced as you move toward higher latitudes. If you lived in Barrow, Alaska, for example, July ends with the Sun above the horizon for 24 hours; by the end of August the length of daylight is over 8 hours less! 2026. The earlier sunsets mean that we don’t have to wait until late evening to enjoy the astronomically dark sky. It is a great time to enjoy summer’s celestial offerings in their full splendor. Astronomical twilight now ends at around 9:30 pm local time, and the rest of the evening hours are prime time to take in the sights of Scorpius, Sagittarius, the Summer Triangle, and the soft glow of the Milky Way. At this time you will find Scorpius above the southwest horizon, led by the bright ruddy-hued star Antares. If the night is clear and free of haze, go to a dark location and trace out the figure of the Scorpion. Four thousand years ago, when the ancient Egyptians first described the constellation, it was much higher in the sky than we see it today. This is due to the 26,000-year cycle known as precession, which causes the stars to slowly shift westward along the ecliptic plane. That said, we can still get a good view of its distinctive shape which, with a small amount of imagination, traces a decent figure of its namesake. The area above the Scorpion’s “tail” is the general direction of the center of our Milky Way galaxy, and it is a splendid region of the sky to examine with binoculars or a small telescope. There are dozens of star clusters and glowing clouds of nebulosity visible as you pan up along the Milky Way’s plane. Many of these are clusters of newly-formed stars, and the glowing clouds of gas are stellar “nurseries” where new clusters will emerge. Take some time to look carefully at the general glow of the Milky Way itself. In a small low magnification telescope the fuzzy bands resolve into uncountable masses of faint stars. When I find myself in an open field, gazing at these masses of faint stars that fill the eyepiece, I often wonder if there are more stars like our Sun, hosting planets like Earth, and whether there is something there looking back at me and pondering the same thought. If you are out around half an hour after sunset, look to the western horizon to try to spot the bright glow of the planet Venus, slowly making her way into the evening sky. She has been lurking in evening twilight for the past month, but over the course of the next several weeks she will gradually outpace the setting Sun. By the end of September she will set at the end of evening twilight, and by the end of the year she will dominate the evening sky. Saturn rises with the bright disc of the waning Moon as the week opens, and continues to work his way into the evening sky. He will reach opposition, rising at sunset and setting at sunrise, on September 8th. By 11:00 pm he is prominent in the southeastern sky among the faint stars of Aquarius. His subtle yellow hue should easily distinguish him from the star Fomalhaut, some 20 degrees to the south. Jupiter now rises at around 1:00 am local time. He brings his cheery glow to the rising stars of the Winter Circle, which should also be visible as morning twilight begins to gather. As the week opens you will find the ruddy glimmer of Mars just three degrees east of Old Jove. During the course of the week the red planet will drift some five degrees farther eastward, from the giant planet, leaving him among the stars of Taurus. Be sure to catch the two planets and the Moon together before sunrise on the 27th.