Jupiter and Saturn Form Rare Visible 'Double Planet' Not Seen in 800 Years

A celestial event is taking place this month that hasn’t occurred since the Middle Ages. Jupiter and Saturn are expected to be so close to each other that they will form the first visible “double planet” seen in 800 years, according to astronomers.

"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," Rice University astronomer Patrick Hartigan said in a statement, according to CBS News. "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.”

It's a spectacle worth viewing, and for those who would like to witness it, here are some additional details.

How close will the two largest planets in our solar system be, exactly? The two planets will be just 0.1 degrees apart - less than the diameter of a full moon, EarthSky reported. 

When is this historic event taking place? The event aligns with the December solstice, on Dec. 21, 2020, marking the shortest day of the year in the Northern hemisphere. 

Where can I see this? As long as the sky is clear, it's observable from anywhere on earth, said Rice University astronomer Patrick Hartigan. The further north you are, the less time you’ll have to catch a glimpse of the conjunction before the planets sink below the horizon, he explained.

For how long will this go on? Through the month of December, skywatchers can look up each night and watch the two planets get closer and closer. Hartigan said the best time to view the planets is during twilight hours, when they will be bright and more visible. 

How do I know which planet is Jupiter and which is Saturn? Both planets are very bright. According to experts, Jupiter appears brighter than any star in the sky. Saturn is slightly dimmer. Saturn will appear just to the east of Jupiter, and will even look as close to the planet as some of its own moons.

What happens if I miss it. When can I view it again?  Looks like March 15, 2080, is when Jupiter and Saturn are expected to be "this close" together in the night sky. After that, according to Hartigan, the pair won’t make such a close appearance until sometime after the year 2400.

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