- Jupiter and Saturn will align in the night sky on December 21st.
- The two planets only align every two decades or so.
- The planets will appear so close that they’ll look like a “double planet” according to astronomers.
What are you doing to be doing on the evening of December 21st? Dreaming about all the awesome holiday gifts you’re going to get? Frantically last-second shopping for those gifts for someone else? Or maybe just binge-watching some Netflix because I mean, what else is there to do when there’s a pandemic happening?
Well, if you end up not doing any of those things, you could take some time to gaze skyward and see a sight that is only possible every two decades or so. On that night, two of the largest planets in our solar system — Jupiter and Saturn — will be nice and close. In fact, they’ll be so incredibly close that they’ll appear as a “double planet,” according to astronomer Patrick Hartigan of Rice University.
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Because of the nature of how planets orbit the Sun, the proximity of any two planets to one another varies wildly over the course of many years. In the case of Earth and Mars, our two worlds are only close enough to launch missions from our planet to the Red Planet every two years or so. For Jupiter and Saturn, the two planets only “line up” from our point of view every 20 years or so.
That being said, the night of December 21st will be particularly special thanks to how close the two planets will appear. In fact, it’s been hundreds of years since the two planets will align in the skies as they will in a few weeks.
“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another,” Hartigan said in a statement. “You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky.”
That’s a long, long time, and probably a good reason to take a moment to gaze skyward. If you have even a hobbyist-level telescope, you should have a pretty good shot at seeing it, assuming the weather is cooperating. The closer you are to the equator, the better the view will be.
“On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” Hartigan explains. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”
Mark your calendars, because 2020 might actually give us something we want for once!