Sky Tour Podcast for December 2024

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.
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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 December. In this episode we’ll mark the solstice, be amazed by Jupiter, welcome the arrival of winter’s bright stars, and prep for what’s usually the year’s best meteor shower. So grab your curiosity, bundle up, and come along on this month’s Sky Tour.
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I’m a Californian who ended up in New England, and I am not a big fan of cold, snowy winters. So I’ll rejoice when it’s 4:21 a.m. Eastern Standard Time on December 21st. That will mark a celestial turning point: the solstice. This Latin word means “Sun stands still.” At that moment the Sun has traveled its farthest south in the sky, shining directly down on Earth’s Tropic of Capricorn in the Southern Hemisphere, and then reverses direction to gradually move northward among the stars. This date marks the astronomical beginning of summer in the Southern Hemisphere and of winter up here in the north. For those of us at mid-northern latitudes, around this solstice the span from sunset to sunrise is at least 14 hours. That’s great for stargazing, of course, but a little depressing if you love being out in the sunshine. 
Meanwhile, the Moon will once again glide through its phases in close sync with the calendar. In fact, new Moon occurs early on December 1st, followed by first quarter on the 8th. Then it fills out completely to the full Cold Moon, rather obviously — early on December 15th. Last quarter follows on the 22nd, and we get a bonus new Moon on December 30th. So, to calibrate your internal celestial clock, you’ll have the Moon in the evening sky during the first two weeks of this month.
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It’s going to be a fun month for planet-watching. Let’s start with Venus, which is well up in the southwest as evening twilight fades, and it’s gradually getting higher. By month’s end it’ll set almost four hours after the Sun. Venusa is truly brilliant — it’s at least a dozen times brighter than any other nighttime star. Sometimes you might hear it called the Evening Star, though of course it’s not really a star, and it’s mistaken more times than you might think for a UFO — or, in current-speak, an unidentified aerial phenomenon. But of course we skywatchers know exactly what it is, right?
Once it gets good and dark, look diagonally to the upper left of Venus, higher up toward south, and you’ll bump into Saturn. Now, this is not the most dazzling of planets, so don’t worry if you have to look around a bit to find it. But there’s an easy way to spot Saturn — just follow the Moon! Its razor-thin crescent skirts past Venus on the 4th, then three nights later, on the 7th, you’ll find the Moon to the lower right of Saturn. The later you look, and the farther west you live, the closer the two will be. By the time the Moon sets as seen from San Diego, it’ll be less than 2° from Saturn.
But now let me introduce you to the headliner for this month’s planet parade. As it gets dark, turn around so your back is toward where the Sun set and feast your eyes on brilliant Jupiter rising low in the east. Jupiter can’t quite match the brilliance of Venus, but right now it comes pretty close. On December 7th, the King of Planets reaches opposition, meaning it appears opposite the Sun in our sky. It also means that Jupiter is just about as close to us as it can get. On this date Jupiter rises when the Sun sets and vice versa, and it stays in view all night long.
As you watch Jupiter, make a mental note of where it is with respect to the horizon, and check the time. Then look in that same spot 4 hours later, and you’ll be greeted by another bright planet — Mars. It’s bringing up the rear in this month’s four-planet parade. Now, circle December 18th on your calendar: that morning, in the hours before dawn, the waning gibbous Moon passes within ½° of Mars. They’ll make a dramatic pair.
By mid-January the Red Planet also will reach opposition, so next month you’ll have a chance to see Venus, Saturn, Jupiter, and Mars all at once.
The only bright planet that’s missing is Mercury, but December offers a good chance to see it as well. You’ll need to be up before dawn during the final days of 2024. Look toward southeast starting about 45 minutes before sunrise. Mercury is making its best predawn appearance of the year, so spotting it should be fairly easy. On the morning of the 28th, it’ll be joined by a very thin crescent Moon off a bit to its right. That should be a nice pairing indeed.
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Wow, our solar system is putting on quite a show this month. But what about the stars overhead? Remember them? Early in December, once it gets good and dark — say, around 7 p.m. — the majestic stars of Orion veritably leap up over the eastern horizon, following Jupiter up into the sky. By month’s end, those same stars come into view a couple of hours earlier, soon after sunset. Look for the Hunter’s distinctive belt of three stars, oriented as a vertical row as the constellation climbs into the sky. The belt is flanked by ruddy Betelgeuse to its left and icy-white Rigel to its right.
Just a bit to Jupiter’s right is a modestly bright star showing the slightest hint of red color. This is Aldebaran, the angry eye of Taurus, the Bull. It’s a red-giant star about 44 times the Sun’s diameter and more than 500 times its brightness. Aldebaran doesn’t seem that bright because it’s 65 light-years away. In other words, the light from Aldebaran that’s hitting your eye left that star in 1959, when Dwight Eisenhower was president of the United States and the Soviet Union’s Luna 3 spacecraft took the first-ever images of the Moon’s farside.
Aldebaran has been known by many names over time. Ancient Persians knew it as Tascheter, one of four stars that guarded the heavens, and the Romans called it Parilicium. If you’d lived in the Middle Ages, you might have used Cor Tauri, meaning “heart of the bull”. Hindu astronomers know it as the lunar mansion Rohini, meaning “the red one”. 
But the name Aldebaran is Arabic for “the follower.” And what is this star following? That would be the Pleiades, seen higher up in the evening sky by about the width of one fist. It’s a small fuzzy spot. But look harder, and you’ll realize that it’s actually a little cluster of stars, small enough to cover with the tip of your little finger. How many individual stars can you count in the cluster? Five or six? Seven? Another name for the Pleiades is the Seven Sisters, and I’ll have more to say about them next month. But get this: the Japanese call this cluster Subaru — yep, just like the car. In fact, next time you see a Subaru on the street check out the logo: it’s a stylized star cluster. Aha!
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Finally, December features the return of what’s often the very best meteor shower all year: the Geminids. This shower reliably delivers upward of 100 meteors per hour radiating from a spot near Castor in Gemini. Unfortunately, this year the nearly full Moon throws a damper on the viewing conditions, but even so a few of the brightest meteors should shine through the moonlit sky. The radiant is well up in the sky by 9 or 10 p.m. as seen from mid-northern latitudes and is highest overhead around 2 a.m. For North Americans, the best nights to look will be the 12th and 13th.
Geminid meteors come from 3200 Phaethon, an asteroid discovered in 1983 that circles the Sun every 3.3 years. This relatively tight orbit keeps particles shed by the comet relatively close together, so we get a display of “shooting stars” that’s stronger than typical shower meteors. Phaethon isn’t very large, only about 3 miles across, but it approaches the Sun closer than any other named asteroid — only 13 million miles away. That’s well inside the orbit or Mercury, and it means temperatures on Phaethon can climb to more than 1,300° Fahrenheit. Astronomers think this body’s rocks start cracking and breaking down into dust as the searing sunlight heats its surface. The Sun’s radiation pressure then drives them off into space. And when some of them slam into our atmosphere at 22 miles per second — bam! — we get a nice cascade of shooting stars.
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That’s our Sky Tour for this month, so thanks for letting me expand your celestial horizons. 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.
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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 we’ll spend some quality time with the Pleiades. Until then, I wish you Clear Skies.