Still Plenty of Summer in the Heavens!
This month, summer officially ends, but plenty of summer constellations are still playing on stage in our nightly celestial theater. As a bonus sunsets are earlier, so your stargazing time is expanding! The autumnal equinox this year is on September 22nd at 19:11 universal time. That’s the moment the sun is shining directly over the Earth’s equator. Days and nights are nearly equal in length.
Without a doubt the first half of the month will be best for serious dark sky stargazing. After that, moonlight will get in the way. In fact, on September 20th, we have a full moon. Since it’s so close to the autumnal equinox, that officially makes it the Harvest Moon in 2021. Because of unique celestial mechanics this time of year, the moon rises only about 20 minutes later each evening, making the full moon seem to “last longer” this month.
The great Jupiter-Saturn show continues in the southeast evening sky. Both planets reached their minimum distances to the Earth last month, but honestly they’re still just about as close. On top of that, both planets are a little higher in the sky as darkness sets in and less susceptible to the blurring effects of Earth’s atmosphere near the horizon. You can’t miss them. They’re the brightest starlike objects in that part of the sky and can’t wait to be viewed through telescopes. Jupiter is the brightest of the two planets. The next brightest “star” a little to the right of Jupiter is lovely Saturn. Around mid-month, the nearly full moon will be hanging close to the dynamic duo of our solar system. On September 16th, the moon will be hanging just below and to the right of Saturn. On the 17th, the moon will be just to the lower right of Jupiter.
Even if you have a smaller, less powerful telescope, you can have a lot of fun with both planets. To really get the most observing bang for your buck, make sure you take long continuous views of ten to fifteen minutes. You’re bound to see more detail as your eye gets used to the light level inside the eyepiece. You might also catch little pockets of less turbulent air, leaving you with a clearer view.
Direct your telescope or even a pair of binoculars at Jupiter, and you should easily resolve the disk of the 88,000-mile-diameter planet. You might even see some of Jupiter’s cloud bands. You’ll undoubtedly see up to four of Jupiter’s brightest moons that appear as tiny “stars” on either side of Jupiter. They continuously change their arrangement from night to night as they orbit Jupiter in periods of two to seventeen days. Some nights, one or more may be hiding behind the giant planet or camouflaged in front of it.
Saturn is an absolute gem to see with a telescope! Without any trouble, you should be able to make out Saturn's enormous ring system, made up of billions and billions of bits of ice. You’ll also spot Saturn’s largest moon, Titan, and maybe some of its dimmer moons, too. If you want to get a young person excited about amateur astronomy, have them look at Saturn through a telescope. They’ll be hooked!
Venus is actually the brightest planet in the early evening sky, but it’s not out for long. It pops out in the very low western sky in the evening twilight and sets less than an hour or so afterward. On September 9th, a thin, waxing crescent moon will be poised just to the upper right of Venus. To be candid, I find that looking at Venus through a telescope is not all that exciting because of its complete and poisonous cloud cover. This month, for extra credit, see if you can spot Mercury in the first half of September, extremely close to the western horizon.
Summer constellations still dominate much of the sky. The asterism known as the summer triangle is nearly overhead in the early evening. It’s made up of the three brightest stars you can see near the zenith. It’s a great tool to help you navigate that part of the sky because the three stars — Vega, Altair, and Deneb — are all the brightest stars in their respective constellations, Lyra the Harp, Aquila the Eagle, and Cygnus the Swan, otherwise known as the Northern Cross. From those three constellations, you can branch out with your eyes to find other surroundings, fainter constellations like the delightful Delphinus the Dolphin and several others.
In the low south-southwest sky, not far from Jupiter and Saturn, are the classic constellations Scorpius the Scorpion and Sagittarius the Archer. Scorpius actually looks like a scorpion. Sagittarius is also known as the “Little Teapot” because that’s what it really resembles.
If you’re stargazing in the dark countryside, you’ll see a milky band of ghostly light that bisects the sky, running in an arc from the low southern sky up to the zenith and then down to the northern horizon. That’s the Milky Way band, made up of the combined light of the billions and billions of stars that make up the plane, or the thickest part, of our own Milky Way Galaxy. The center of our home galaxy is in the direction of the spout of the Sagittarius teapot. If it weren’t for opaque interstellar gas and dust, that part of the Milky Way band would be much, much brighter. If you want to really treat yourself, lie back in a reclining lawn chair with a pair of binoculars and slowly pan the entire Milky Way from horizon to horizon. You’ll love it!
The Big Dipper is hanging by its handle in the northwest sky, outlining the derrière and tail of the constellation Ursa Major, the Great Bear. The fainter Little Dipper, also known as Ursa minor, is standing on its handle, and at the end of the handle is Polaris, a moderately bright star also known as the North Star.
In the northeast, look just below the bright W that outlines Cassiopeia the Queen, and you’ll see the first of the autumn constellations, Pegasus the Winged Horse. Just look for the “Great Square,” or the diamond of four brighter stars rising in the east that outline the torso of the flying horse. Andromeda and Aries are also on the rise in the early evening.
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul, and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications. Available at bookstores and online at www.adventurepublications.net.
If you have any astronomical questions or want me to write about something you’re seeing in the night sky drop me a line at email@example.com