HOUSTON, Texas — The year 2020 may be something most people look to forget after New Year’s, but astronomers say it will end with one unforgettable sight before it goes. Patrick Hartigan of Rice University says everyone in the world will be able to see Jupiter and Saturn come together so closely they will look like a “double planet” on Dec. 21. The last time the two giant planets aligned like this was 800 years ago!

“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 says in a university release. “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.”

Jupiter-Saturn double planet
A view showing how the Jupiter-Saturn conjunction will appear in a telescope pointed toward the western horizon at 6 p.m. CST, Dec. 21, 2020. The image is adapted from graphics by open-source planetarium software Stellarium. (This work, “jupsat1,” is adapted from Stellarium by Patrick Hartigan, used under GPL-2.0, and provided under CC BY 4.0 courtesy of Patrick Hartigan)

The astronomer adds that Jupiter and Saturn have been moving towards each other in the night’s sky since this summer. From Dec. 16 until Dec. 25 (Christmas Day), the two planets will appear to be separated by less than the width of a full moon to people on the Earth. At sunset during the winter solstice (Dec. 21), they will look closer than at any point since the Middle Ages.

“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,” the professor of physics and astronomy details. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”

Where can you see this ‘double planet’ event?

Hartigan has good news for anyone on planet Earth looking to catch this sight. While the best place to view the “double planet” will be around the equator, people looking towards the horizon in any country will see the show, weather permitting. In the western hemisphere, the planets will pop up about an hour after sunset.

“The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon,” Hartigan explains. “By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon. Viewing that would be manageable if the weather cooperates and you have an unobstructed view to the southwest.”

For sky watchers in New York and London, the planetary alignment will be found between 5.3 and 7.5 degrees above the horizon. The astronomer recommends people near these cities start watching the sky right after the sun sets.

If you miss this celestial showstopper, you’d better keep yourself in good health. The next time Jupiter and Saturn will come this close won’t happen until March 15, 2080. Once that alignment passes, Earthlings will have to wait until the year 2400!

About Chris Melore

Chris Melore has been a writer, researcher, editor, and producer in the New York-area since 2006. He won a local Emmy award for his work in sports television in 2011.

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