Jupiter and Saturn Will Align on the Night of the Winter Solstice

If you’ve gotten the chance to look up during the evenings recently, you’ve probably gotten at least one opportunity to see Jupiter and Saturn relatively clearly in the night sky. The two planets have been particularly visible throughout much of the later part of this year, especially throughout the past several weeks. However, come December 21, 2020—the night of the winter solstice—the two planets will visibly align in what’s known as a planetary conjunction.

Saturn (top) and Jupiter (below) seen December 13 from Shenandoah National Park in Luray, Virginia. NASA/Bill Ingalls

Conjunctions happen when two planets or other astronomical objects appear closely together in the sky from our perspective here on Earth. Effectively, their respective orbits line up with ours. While planetary conjunctions are not necessarily uncommon overall, this particular one has been dubbed the “Great Conjunction” due to its rarity and the date on which it falls. A conjunction of Jupiter and Saturn happens every 20 years or so, but one this significant—with the two planets appearing one-tenth of a degree apart, according to a NASA brief—hasn’t happened for nearly 400 years. And on top of that, it’s been nearly 800 years since it has occurred at night, to say nothing of it happening on the longest night of the year.

“Conjunctions like this could happen on any day of the year, depending on where the planets are in their orbits,” Henry Throop, astronomer in the Planetary Science Division at NASA Headquarters, explained in a press release. “The date of the conjunction is determined by the positions of Jupiter, Saturn, and the Earth in their paths around the Sun, while the date of the solstice is determined by the tilt of Earth’s axis. The solstice is the longest night of the year, so this rare coincidence will give people a great chance to go outside and see the solar system.”

While we won’t have to wait another full 400 years for the next great conjunction of these two planets, we won’t see something like this with a similar visibility for another 60 years, in the year 2080, so it’s safe to say that for many of us this will be a once-in-a-lifetime astronomical show.

As Mearle Hiltner of the Minnesota Astronomical Society (MAS) explains in the society’s Gemini Newsletter for this month, “Historically, the great conjunctions have been observed for thousands of years. In fact a great conjunction of Jupiter and Saturn is one of the possible explanations for the star of Bethlehem. Most people may only get three or four chances to see this in their lifetime. To have the opportunity to see the two giants of the solar system in the telescope together is an extremely rare astronomical event.”

For those of us here in the Twin Cities, it won’t be difficult at all to get a glimpse of this event as it happens just as along as you know where to look.

“Jupiter and Saturn are the two bright stars in the western sky shortly after sunset,” Dave Falkner, president of MAS, told Twin Cities Geek. “You don’t need a dark spot to view them, just a clear view of the western sky. The conjunction occurs on the 21st, but within a couple of days either side of that you, should be able to capture both of them in the eyepiece of a low power telescope.”

So if you’re a professional or amateur astronomer, a casual stargazer, or just someone with a simple curiosity for the night sky, make a point to look up on the winter solstice.