Jupiter and Saturn will align in the night sky on December 21. It will be the closest they have appeared in 800 years.
The two planets align or conjugate every 20 years. But this year they will be so close that they will look like a “double planet”.
The last time Saturn and Jupiter were this close and visible was in 1226.
These are the best ways to see this conjunction.
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Jupiter and Saturn are about to align perfectly in the night sky; The two planets will get so close on December 21 that they will appear to touch.
The last time they looked this closely from Earth’s point of view was almost 800 years ago, on March 4, 1226.
An astronomical event in which the heavenly bodies align is called a conjunction. Since this conjunction involves the two largest gas giants in our solar system, it is known as the “grand conjunction.” It happens to some extent once every two decades.
“But it is fair to say that this conjunction is truly exceptional in the sense that the planets come very close to each other,” explained Patrick Hartigan, professor of physics and astronomy at Rice University, on his website.
“In fact, they will be so close that it can be challenging to separate them at a glance for many people,” he added.
Here’s how to view this rare conjunction.
How to see a ‘double planet’
A photo of Jupiter captured by NASA’s Hubble Space Telescope on August 25, 2020.
NASA, ESA, STScI, A. Simon (Goddard Space Flight Center) and MH Wong (University of California, Berkeley) and the OPAL team
On the night of the winter solstice, Jupiter and Saturn will be separated by a distance in the sky equal to about one-fifth the diameter of a full moon, according to Hartigan. They will appear to form a “double planet”.
Of course, the two planets are much further apart than that, more than four times the distance between the Earth and the sun. But to our eyes, they will look like a single point of bright light.
If you look through a small telescope, Jupiter and Saturn will appear in the same field of view, along with some of their moons.
How Jupiter and Saturn will appear in a telescope installed in Houston, Texas, on December 21, 2020 as they approach in the sky.
Patrick Hartigan / Rice University / Adapted from Stellarium graphics
However, it will be challenging to see this conjunction in the United States, Canada and Europe, Hartigan said, because of how low it will be on the horizon in the Northern Hemisphere.
“Observing conditions are best near the equator, although no matter where you are, there may be an hour or so to observe this conjunction before the planets sink into the haze,” he added.
If you go out around twilight, the hour after sunset, and point your telescope toward the southwestern sky, you can detect the event, Hartigan said. (Websites like Stellarium can help you point your telescope towards the meeting point of the planets.)
“You will need to have a clear southwest horizon with no low clouds in the distance,” Hartigan said.
He recommends setting up your telescope before it’s completely dark and bringing binoculars.
If the night of the solstice ends up cloudy where you are, Hartigan said, don’t worry: the conjunction is an ongoing event from Dec. 17-25. The 21st is just when the two planets will be closer in the sky. .
Another conjunction like this will come in 2080
In the past 2,000 years, there have only been two times when Jupiter and Saturn came closer in the sky than they will be this year.
One of them was in 1623, but the glare of the sun made it impossible to see. However, if this next rare conjunction is missed, another will come in 60 years.
A photo of Saturn and two of its moons, taken by Voyager 1 in 1980.
SSPL / Getty
On March 15, 2080, Jupiter and Saturn will look as close as they do this year. That event will be much easier to watch, according to Hartigan, because it will take place higher up on the horizon.
“The biggest challenge is that you will have to live another 60 years to see it!” he said.
