Jupiter, Saturn will look like a double planet on December 21 in rare celestial event

© NASA, ESA, A. Simon (Goddard Space Flight Center), MH Wong (University of California, Berkeley) and …
Photos of Jupiter, left, and Saturn, right, taken by the Hubble Telescope in 2019.

It happens in December and it is literally a once in a lifetime sight.

Jupiter and Saturn will look like a dual planet just after sunset on December 21 because the two planets will be in conjunction, also known as the “great conjunction,” said Amy Oliver, spokesperson for the Harvard-Smithsonian Center. for Astrophysics.

“Most adults have never seen such a conjunction and they won’t have the chance to see it again,” Oliver said in a telephone interview on Wednesday.

Although this conjunction occurs once every 20 years, it is even rarer – the two planets will appear to be on top of each other because they will be 0.1 degrees away – about a fifth of the moon’s diameter. – each other, Oliver said.

The last time the two planets seemed to be this close was in 1623, 14 years after Galileo created his first telescope, Oliver said. However, at the time, people couldn’t see it due to its proximity to the sun, blocking the view.

“Only astronomers would have really known about it, but they didn’t have social media to tell people, ‘Hey! Look at this! “She says.

The last time people would have noticed this close conjunction would have been in 1226, in the Middle Ages, almost 800 years ago.

This also happens during the December solstice, adding even more to its rarity, she said.

The two planets have been approaching Earth’s sky for some time now, Oliver said. For more than a week, they will be separated by less than the diameter of a full moon, with December 21 being the closest approach.

If you watch now, you can already see it in action.

“It’s like teenagers at a dance in high school – they’re getting closer and closer,” Oliver said. “It’s been a year watching this, getting closer to them, and now they’re going to dance in slow motion.

Jupiter and Saturn will be at their closest alignment around 1:20 pm EST on December 21 and will be visible in the daytime sky with a “very good pair of binoculars or a backyard telescope,” if the time permits, Oliver said.

The two planets will still be visibly close to each other when it gets dark, or shortly after sunset, to Boston viewers, before it appears below the horizon, Oliver said.

The next time for the chance to see Jupiter and Saturn so close to each other, but higher in the sky, would be March 15, 2080, Oliver said.

In other words, don’t miss a thing.

“2020 has been a great year for astronomy and a lot of really wonderful things have happened in the night and day skies,” Oliver said. “Partly, we’re so focused on everything that hasn’t been so great in 2020 that we forget to enjoy those moments that are much bigger than what we attribute to them.”