It hasn’t happened in nearly four hundred years. Over the course of the last month, the great gas giants Jupiter and Saturn have been approaching each other in the night sky. On Monday, December 21—the evening of the winter solstice—the two planets will align, their reflected light merging into a single point in the night sky. Astronomers call this type of event a conjunction, and your next chance to see Jupiter and Saturn so close together won’t be until 2080.
“From the naked eye, the conjunction will look almost like the two planets are merging into one point of light,” says Stephen Hummel, dark skies specialist at the University of Texas’s McDonald Observatory in Fort Davis. “But an amateur telescope will also let you see Jupiter’s moons around it, and a really good telescope will let you see Titan, the moon of Saturn. Their moons look like they almost intermingle, in a way.” You don’t have to wait until December 21 to watch the conjunction; start looking up now, and you’ll see the planets inch a little closer each night.
This cosmic event is remarkably rare, Hummel says. While Jupiter and Saturn do pass each other in the sky every twenty years, they almost never appear to be this close to each other. The planets will appear at their closest since 1623, when Francis Bacon was devising the scientific method. (Prior to that, the last conjunction you’d have been able to actually see occurred during the Middle Ages, in 1226.) Since this one is coincidentally happening on the solstice, some have nicknamed it the Christmas Star.
The rarity of such conjunctions made them fascinating to ancient astronomers and astrologers across the globe. Jupiter and Saturn are the slowest “wandering stars” in the night sky, and as historian Ali A. Olami wrote on Twitter, ancient stargazers including the Greeks and Babylonians associated their movements with momentous events. For medieval Muslim astrologers, conjunctions between the two planets often “represent the rise and fall of empires, the coming of messiahs, and … the apocalypse,” and writers—including fourteenth-century European authorities who drew from translated Muslim texts—claimed that such conjunctions foretold the rise of the Mongols, the Black Death, and other cheery events. (Since astrology isn’t real, the conjunction’s presence at the tail end of 2020 is fine. Probably.)
If you’d like to witness this event of vast cosmic significance, foretelling the damnation of the American empire and the dawning of a new Aquarian age—or just use this as an opportunity to get out of the house and start paying a bit more attention to the night sky—Hummel shared a few tips with Texas Monthly.
What if I just want to see the conjunction?
Make sure you’re at your preferred star spot by sunset, which on December 21 will be around 5:30. Start by looking southwest: the planets will appear low in the western sky for about 45 minutes to an hour. Even if you don’t have any gear, you’ll be able to see them with the naked eye.
Gear sounds cool, though. What should I use?
It does generally help to have some sort of optical aid. But Hummel recommends binoculars over a telescope for novice astronomers. “A nice pair of binoculars costs as much as a not very nice telescope,” he points out. Binocs might not always show you Saturn’s rings, but they’re great for starting out. (The most important type of optics, Hummel emphasizes, are the ones you’ll actually use: a fancy telescope does nobody any good gathering dust, but binoculars are handy for all sorts of things.) Plus, no matter how nice your optics are, you may want a mount to keep them steady—neck strain is an occupational hazard, Hummel says, and arms tend to shake. A mount is useful even if you’re just using a pair of binoculars. “You don’t want to skimp on that. It’ll save you a lot of frustration down the road.”
Many tripod mounts and telescopes are currently out of stock because of surging demand during the pandemic, but if you only want to see the conjunction, you shouldn’t need them. Just remember to stretch.
This is fun! But how do I hear about other cool space things?
Hummel recommends using Stellarium, an open-source planetarium software that explains when objects in the night sky rise and set, and what stars, meteors, and other cosmic phenomena will be visible at a given time. (The web and desktop versions are free, or you can shell out $9.99 for the smartphone app.) There’s also a wealth of publicly available information on stardate.org, whose offerings include a daily public radio broadcast, and Sky and Telescope magazine shares information for a variety of skill levels. And if you want to talk to other amateur astronomers, you can always check out the forums at Cloudy Nights.
Where should I go?
That depends on what you want to see! Planets, the moon, and bright stars are the same in the city as they are out in the countryside, and even with light pollution you can see more than you’d think, Hummel says. If you want to see fainter cosmic phenomena—star clusters like the Pleiades, nebulae, and galaxies far, far away—it helps to go out to darker skies, such as those found in the countryside or in designated dark-sky communities like Dripping Springs, just southwest of Austin. Keep in mind where the celestial objects are going to be appearing in the sky as well: going up on a hillside won’t make the stars and planets clearer, but it’s hard to see the night sky when there’s a building in the way.
Okay, but how do I actually look at the stars?
The key to success here lies in understanding how human eyes work in the dark, Hummel says. Unlike most mammals, humans can see in color—but our color vision works best in well-lit conditions. At night, our vision switches to primarily black and white. Full night vision takes a while to kick in—up to thirty minutes, in some cases—and you can ruin it just by looking at your phone screen for a few seconds. Hummel recommends either putting a red screen filter on it or, preferably, leaving it in your pocket. You might also consider using a headlamp or flashlight with a red-light setting.
When scanning the sky for fairly bright objects, such as planets, you can generally pick them out just by looking directly at them. But if you’re seeking something faint, remember that your peripheral vision is much more sensitive to light than the center of your eye is. Faint stars—like ghosts—have a nasty habit of disappearing when you look at them directly. “If you’re trying to see something faint, and you’re not sure if you see it, look slightly away from it,” Hummel says. This is called “averted vision,” and while it takes a bit of practice, it’s a very important trick: most astronomy books and magazines take a stargazer’s skill at it for granted.
All I can see is the moon!
The moon is a much bigger factor in astronomy than people expect, Hummel says. A full moon in the sky throws off almost as much light as the ambient glow of a city. So if you’re planning to drive out to the inky black skies of the country to look for the faint glimmers of a distant nebula, and you don’t time it correctly, you’re going to end up very frustrated. For best results, choose a moonless night for your stargazing jaunt. “The moon’s good to look at, but it does steal the show,” Hummel says. You won’t have to wait long for the next new moon, which is on December 14.
But why doesn’t it look like it does in National Geographic?
It’s important to have realistic expectations. Astronomy pictures tend to be taken with very powerful cameras, which are significantly better at penetrating the inky depths of space than is the human eye. (And remember, our eyes are very bad at seeing color at night anyway.) “Things aren’t going to look like some of the pictures you see online,” Hummel says.
But if that disappoints you, think of it this way: When you look up on the December 21, you aren’t just looking at two points of abstract light becoming one. You’re glimpsing a moment when two of our solar system’s largest worlds—each hanging millions of miles apart in the black void—line up with ours, so that even their moons seem to dance in step with one another. Generations of people have mapped the clockwork wanderings of celestial spheres: look up and you’re seeing something that has awed medieval scholars, Babylonian priests, and Greek storytellers alike. And you don’t even have to worry about the vast omens authored by an invisible hand across the velvet emptiness of the sky.
You know. Probably.