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Jupiter and Saturn will appear their closest since the days of Galileo in this rare space event.

USA TODAY

This year’s winter solstice will bring a rare sight to our night skies — just in time for the holidays.

For Earth viewers, Jupiter and Saturn will appear closer to one another on Dec. 21 than they have been since the Middle Ages. If you can gaze into the southwestern horizon at the right time, the two gas giants will look like neighboring points of light.

Almost a “double planet,” said Rice University astronomer Patrick Hartigan.

“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 explained.

“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.”

Astronomers call what we’ll witness on Dec. 21 a “conjunction.” From asteroids or moons to planets and stars, a conjunction is when two objects in space appear to be close to one another, as observed from Earth. In the reality of space, they’re still hundreds of millions of miles apart.

Every 20 years, our solar system’s largest planets align during their orbits around the sun. Jupiter and Saturn’s last conjunction was in 2000. But this year is particularly special because the two will appear to separated by just 1/5th the diameter of a full moon — or 0.1 degrees — an occurrence the world hasn’t seen since the Middle Ages.

The last time Jupiter and Saturn came this close was 1623, but that conjunction was too near the sun to be seen by Earthlings. Therefore, 1226 is actually the most recent time that such a close conjunction of Jupiter and Saturn was visible to humans.

“That’s just sly of 800 years ago” said Amy Oliver, spokeswoman for the Harvard-Smithsonian Center for Astrophysics.

“Call [2020’s conjunction] a unique, holiday gift to the world,” she said. “Maybe it’s the soothing band-aid for 2020.”

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How to watch the 2020 conjunction on Dec. 21

Saturn and Jupiter are already visible in December’s sky, as the two planets have been moving closer to each other for much of 2020. They will look like two points of light in the sky — Saturn, which is farther from Earth, will be the fainter one.

Both Hartigan and Oliver encourage stargazers around the world to start looking now.

“Over the next couple of weeks you can watch them move which is super cool, because you’re actually seeing planets in orbit” Hartigan told USA TODAY, adding that identifying them now will also make the conjunction on winter solstice easier to identify. 

And to witness the conjunction on Dec. 21? Weather permitting, it