Visible planets, the autumnal equinox, and the Harvest Moon! See highlights of the September night sky from The Old Farmer’s Almanac astronomer Bob Berman.
Bright Planets of September
by Bob Berman, as featured in The 2021 Old Farmer’s Almanac
Oh, what a night! The mild evenings of September are perfect for planet and stargazing. Even better, we find that planets Venus, Jupiter and Saturn are bright and visible in the evening all month long!
At twilight, a nice series of conjunctions happens in the west his month.
- On the 1st, dazzling Venus is to the upper left of Mercury, with that innermost planet very low but bright at exactly magnitude 0.0. On the 8th, look for Mercury below the thin crescent Moon.
- On September 9, at dusk, the young Moon will stand to the upper right of Venus. The bright planet appears just about the horizon.
The crescent Moon and Venus. Credit: NASA/Bill Dunford
- Then, on September 10, after sunset, look again for the crescent Moon; Venus appears to its lower right, very near the bright double star Spica. Mercury will be nearby, low near the horizon, though you may need binoculars to find it.
How the Moon and Venus will appear on September 10, 2021. Credit: NASA/JPL-Caltech
- On Tuesday, September 14, Neptune reaches opposition. Neptune will be visible all night–so it’s as good as chance as any to spot Neptune. This is the only planet in our solar system that is not visible to the naked eye, so you will need a pair binoculars or small telescope. I’ll write more about Neptune’s opposition later.
- Mark September 16 and 17 on your calendar. On the 16th, the Moon floats below Saturn, and then appears to hover right below Jupiter on the 17th! See this article from EarthSky to see a great chart and learn more.
Full Harvest Moon
September 20 brings the Full Harvest Moon—just two days before the fall equinox. (The full Moon that happens nearest to the autumnal equinox always takes on the name “Harvest Moon.”) Learn more about the Harvest Moon (a true astronomical phenomenon) and why it’s so special!
September 22 brings transition from summer to fall! Officially, autumn begins at the moment of the equinox—3:21 a.m.on the 22nd. Learn more about the first day of fall in the Northern Hemisphere!
Pegasus Shines in September
This month, watch for Pegasus, the Winged Horse in the southeastern sky! A useful guide to this asterism (unofficial star pattern) is the Great Square, which outlines Pegasus’ body. See our star chart and how to find Pegasus.