As we awaken to summer’s turn toward autumn, Sirius, the brightest star visible from Earth, appears close above the southeast horizon in early morning twilight, marking the change of season. Sirius the Dog Star is familiar to us as Orion the Hunter’s brilliant companion on winter nights. Sirius rises in the east-southeast close to 4 a.m. In a clear blue sky, its twinkling light may be enjoyed in the southeast after all other stars have vanished in the sunrise glow, until about 6 a.m.
As illustrated, above left, today and tomorrow, August 31 and September 1, about 5:30 a.m. to 5:50 a.m., be treated to a glimpse of a delicate crescent moon with planet Mercury (0.05 magnitude) rising above the hills in the east-northeast, fading as twilight brightens.
Now, imagine the lead diagram of Orion and Sirius inserted below Jupiter in this schema. Orion’s Betelgeuse (0.43m), a red giant star, lines up below Jupiter (-2.27m), followed by Sirius (-1.5m). To the right, bluish-white Rigel (0.15m) marks Orion’s knee. Look for these four bright lights as they persist in the brightening blue sky, while all the others fade. Note: The smaller the number the brighter the celestial object. Sunrise 6:18 a.m. on the 31st and a minute later every morning.
Vital statistics for September 1: Twilight 5:50 a.m.; sunrise 6:19 a.m.; sunset 7:30 p.m.; evening twilight 7:57 p.m.; darkness 9:07 p.m.; day length 13 hours, nine minutes.
Having observed the waning crescent moon rising in the east with morning planets (diagram #2), here we welcome the waxing crescent moon in the evening sky, in the west-southwest, poised to set close to planet Venus (-3.91m) and bright Spica (0.96m). The brilliant Evening Star is visible for a very short time after sunset. Sunset on the 5th, 7:21 p.m.; on the 6th, 7:19 p.m. Venus sets at 8:18 p.m on the 5th, 8:17 p.m. on the 6th. Find a location with a clear view to the horizon.
Even as we adapt to changing conditions on Earth—for example, the first frost date at my location in 2023 was November 1, whereas frost was formerly predictable at the end of September—the heavenly bodies remain constant. The Full Harvest Moon rises due east at 6:57 p.m. on September 17 as the sun sets at 7 p.m. due west. Moonrise promises to be extraordinary, a “supermoon” orbiting close to Earth. In hilly locations, rising times are later and setting times earlier.
It is the season of equal daylight and darkness. The autumnal equinox occurs on Sunday, September 22.
