Podcast for October 2024
[[AD BUMPER –]] This month’s episode is sponsored by Celestron, manufacturer of high-quality telescopes and an industry leader in developing exciting optical products with revolutionary technologies.
[[FADE IN – INTRO MUSIC – 60 SECOND BED UNDER 30 SECOND TEASER]]

I’m Kelly Beatty of Sky & Telescope magazine, and tonight we’re going on a tour of the stars and planets that you’ll see overhead during October. In the minutes ahead, we’ll ponder the Moon’s whereabouts; spot a fast-moving comet, learn what Andromeda and Pegasus have in common, circle around the pole star Polaris, and watch for meteors shed by Halley’s Comet. So let’s get going — come along on this month’s Sky Tour!
*****
The Moon’s phases are in sync with the calendar this month, and so keeping track of them will be a snap. We start October with a New Moon on the 2nd. A few days later you’ll see a thin crescent low in the southwestern evening sky, and it’ll grow a little fatter, or wax, and climb higher each night until reaching first quarter phase on the 10th. After that, the waxing continues until full Moon on the 17th, known traditionally as the full Hunter’s Moon. I suppose this was the time of year to go hunting and stock up in preparation for the cold winter ahead. After that the Moon rises later and later after sunset, with its sunlit face getting thinner and thinner, or waning. It reaches last quarter early on the 24th. By then, you’ll see the Moon more easily before dawn. 
It’s easy to think of the Moon as just a circle in the sky, but it’s really a sphere. And its changing shape has nothing to do with Earth’s shadow, as some people mistakenly think. If you’ve ever wondered why the Moon shows different phases as it orbits around Earth, here’s something you can try with a golf ball or a ping-pong ball. Go outside just before sunset in early October, and find the crescent Moon over in the southwest. Hold the ball up at arm’s length so it’s pointed in the Moon’s direction and in sunlight. Now look at the ball. You’ll see a slice of it on the right side illuminated by the Sun, in a crescent shape, while most of it is in shadow — exactly how the Moon looks! 
Do this a couple of nights later, again just before sunset, and you’ll notice that the Moon has moved around in its orbit and appears farther east. Point your ball toward the Moon, and its surface will look more fully sunlit than it did before. It’s waxing, just like the Moon is. Finally, on October 17th, when the Moon is full, hold your ball up in late-afternoon sunlight one more time, toward east where the Moon is about to rise, and it will look “full”.
Here’s the point: The ball and the Moon both show these different shapes because they’re spheres being illuminated by the Sun from different angles. So congrats, you’ve just mastered the mystery of why the Moon goes through its phases each month.
*****
Now if you like a bit of a stargazing challenge, you’re in luck. Right now there’s a comet cruising through the inner solar system, and it’s named Tsuchinshan-ATLAS [soo-chin-shan]. Wow, what a mouthful. Tsuchinshan is the traditional name of China’s Purple Mountain Observatory, and ATLAS stands for the Asteroid Terrestrial-impact Last Alert System in South Africa. These two facilities share credit for the comet’s discovery in early 2023. Honestly, it’s easier just to remember this object’s designation, C/2023 A3 — or just A3 for short.
But I’m not telling you this to improve your pronunciation skills. Instead, this month will be your best chance to spot this interloper, and with luck it’ll become bright enough to see by eye! So here’s the plan. First, you’ll need a viewing location with a completely clear view toward west — no trees, no buildings, no clouds along the horizon in that direction. 
Start looking for the comet around October 13th, or a couple days sooner if you’re got super-clear skies. Watch where the Sun sets, and remember that spot. That’s west, more or less. About 45 minutes after sunset, look off to the left — three times the width of your clenched fist at arm’s length — for brilliant Venus. The closer you are to the equator, the easier it is to spot Venus. I live in the Boston area, and right now I’m envious of anyone living in, say, Miami. Now look three fists above the sunset point for the unmistakably bright star Arcturus. 
Once you’ve spotted these two beacons, you’re almost there! On October 13th, the comet will be almost exactly halfway between them. It’ll appear as a small fuzzy spot, and with luck you’ll see a hint of a tail pointing upward. Use binoculars if you have them. Each evening following the 13th, the comet will be situated a little more to the upper left. Being higher up might make it easier to spot as the twilight darkens, but by then the comet will also be fading.
Just how bright C/2023 A3 will get is a matter of debate among comet specialists. Some speculate that dust in the tail will scatter a lot of sunlight in our direction. It’s like how dust on a dirty car windshield becomes annoyingly bright when you’re trying to drive with the Sun in front of you. If that happens, then the comet will appear much brighter than predicted. So let’s all try to spot this fleeting visitor while we can. For more information, head to skyandtelescope.org for the latest news — and don’t forget to practice your pronunciation: it’s Comet Tsuchinshan [soo-chin-shan]-ATLAS.
*****
I’ve got three other bright planets to track down, starting with Saturn. It’s now a steady presence over in the east after sunset, and it’ll gradually shift westward as the weeks go by. Saturn is a little fainter than usual because its brilliant ring system is tipped almost edge-on to us right now, so they’re not adding much to the planet’s overall brightness. If you need help finding Saturn, it’ll be just to the left of the Moon on the evening of October 13th, and just to its right on the 14th.
Jupiter and Mars are trailing behind Saturn in the sky right now. Jupiter climbs over the eastern horizon by around midnight early in October but by 10 pm at month’s end. It’s unmistakably bright; you can’t miss it. Mars comes up a couple of hours later, situated to the right of the stars Castor and Pollux in Gemini and to the left of Orion, all rising together in the east. A couple of months from now, this panorama of splashy planets and stars will be above the horizon at nightfall. And that, dear listeners, will herald the coming of northern winter. 
*****
Aside from Arcturus, are any other bright stars in view? I’m glad you asked! Look for the Great Square of Pegasus rearing up in the east as it gets dark. It’s three fists to the left of Saturn. The square, which looks tipped up on one corner, represents the body of the mythical horse which, right now, is on its back in the sky. Seems the gods never got around to finishing Pegasus; it’s got a neck and head extending off to the right, and its legs are sticking up toward overhead. But this horse has no behind — it ends at the square’s left corner, a star called Alpheratz — al-FEE-ratz or AL-fer-ratz, depending on who’s saying it. The gods also got a little crossed up here. Alpheratz is actually the anchor star for the constellation Andromeda, which extends off to the left from that point. 
Now make a generous quarter turn to your left, so that you’re facing northwest. See anything familiar over the horizon? It’s our old friend the Big Dipper. We’re used to seeing it higher in the sky, but here it is not far above the horizon. Actually, in this pose, it’s easy to see how the Dipper is just a part of the larger star pattern tracing out the Great Bear, Ursa Major. The bear’s pointy nose, marked by the star Muscida [MUSS-i-duh], is about two fists to the right of the Dipper’s bowl. The bear’s legs dangle underneath, and the farther north you are the more of them you’ll see. Its tail is marked by the arc of three stars in the Dipper’s handle. I’ve never understood why this celestial beast has a long tail — because real bears have stubby ones — and yet many widely separated cultures have recognized this general pattern of stars as a bear. Some historians think its origin as such might date back more than 10,000 years.
Here’s something else to think about. As the starry sky wheels around through the changing seasons, old constellations sink into the sunset, like the Teapot in Sagittarius, and new ones like Pegasus rise in the east. But for star patterns like the Big Dipper, in the northern part of the sky, this seasonal shift becomes a slow counterclockwise rotation around Polaris, the North Star. Here’s your word for the day: circumpolar, which is what astronomers use to describe constellations near Polaris that never rise or set.
Polaris isn’t the brightest star in the sky, but it’s easy to find. Find the two stars on the right side of the Big Dipper’s bowl. Now draw an imaginary line through them, and follow that line upward and to the right until you spot a medium-bright star pretty much all by itself. And what might that be? It’s Polaris, the North Star.
Now use that clenched hand to measure three fists to the upper right of Polaris. You’ll see a group of five stars crudely shaped like a “3”. Or maybe you’ll see them as a broad “W” tipped up on its left corner. The whole pattern is a little bigger than your fist. This is the constellation Cassiopeia, who is a queen in Greek mythology.
You’ll see that Cassiopeia and the Big Dipper are situated on opposite sides of the North Star. So when one is up high, the other is down low. The Dipper dominates in spring and summer, while Cassiopeia rules in fall and winter.
Now look to the upper left of Cassiopeia, and above Polaris, for a wide pattern of five stars looking a little like an upside-down house perched on the point of its roof. This is the constellation Cepheus, who is the husband of Cassiopeia and the mythical king of Ethiopia. About the same distance to the lower right of Cassiopeia are the stars of Andromeda, their daughter.
*****
Here’s one more thing to watch for. Two modest meteor showers come and go during October. The Orionid shower peaks late on the night of October 20th. Now, Orion won’t rise until about 11 p.m., so that’s the earliest you could hope to see any of these shooting stars — which are actually bits of dust shed by Halley’s Comet. You might glimpse a few extra meteors per hour from a dark site late at night and in the hours before dawn. The other is called the Taurids, which are most active the last week of October through early November. Taurus rises in the east a little earlier, around 9 p.m., so keep an eye to the sky when you’re out in late evening on Halloween.
*****
Thanks for letting me expand your celestial horizons for another month. If you want more tips for viewing the night sky, including a free, interactive star chart for any time or date, check out our website, SkyandTelescope.org.
If you haven’t already subscribed, you can find Sky Tour on Apple Podcasts, Spotify, Stitcher, or wherever you listen. And if you’ve enjoyed listening, please leave a rating or review! It will help spread the word about Sky Tour, and I really welcome your feedback.
And if you want to explore the solar system and universe more deeply, check out the full line of binoculars and telescopes available at Celestron.com.
Sky Tour is a production of Sky & Telescope, a division of the American Astronomical Society, and is produced by me, Kelly Beatty.
Next month I’ll explain why queen Cassiopeia is not a happy camper. Until then, I wish you Clear Skies.