Science

Jupiter and Saturn join in the night sky in 'great conjunction.' Here's how you can see it

If you have a keen eye, you may have noticed two fairly bright objects resembling stars low in the western sky after sunset inching closer together. But those aren't stars: they're two planets, Jupiter and Saturn. On Dec. 21, the two will be so close together they'll almost seem to touch.

Planets are the closest they've been in 800 years

Amateur astronomer Alan Dyer photographed Saturn (upper left) and Jupiter (lower right) during twilight on Dec. 3, 2020, from the Allen Bill flats area on the Elbow River in the Kananaskis Country southwest of Calgary, Alta. (Submitted by Alan Dyer/AmazingSky.co)

If you have a keen eye, you may have noticed two fairly bright objects resembling stars low in the western sky after sunset inching closer together over the past month. But those aren't stars: they're two planets, Jupiter and Saturn. On Dec. 21 — the day of the winter solstice — the two will be so close together they'll almost seem to touch.

Jupiter and Saturn — the largest planets in our solar system — have been visible in the sky since spring, with Jupiter being the brighter of the two; it is also the second-brightest planet in the sky after Venus. In the summer, the pair were high in the south, but over the past few months, they've been getting closer and closer, and lower in the southwestern sky.

Astronomers call close pairings of astronomical objects conjunctions. And this conjunction of the two planets is the closest since 1623, making it a "great conjunction" — though that event wasn't visible as they were too close to the sun.

The last time the pair were observed to be this close was in 1226, almost 800 years ago, a time when Ghengis Khan's rule was coming to an end.

How to find them

Astronomers measure the distance between two objects in the sky using degrees. Right now, the two planets are roughly 0.7 degrees apart. But on Dec. 21, they will be a mere 1/10th of a degree apart.

You can measure their close approach over the coming days with your own fingers. Using your pinky finger held at arm's length is a rough measure of one degree of separation. 

 

To find the two planets, you'll need a good view of the southwestern horizon shortly after sunset. And while you don't need any equipment to view it, if you have a pair of binoculars, you'll be able to tease them apart. Viewers with telescopes will get a rare chance to capture the pair in a single field of view.

This image shows Jupiter — with four of its moons — and Saturn during the great conjunction on Dec. 21 as seen through a pair of binoculars. (NASA/JPL-Caltech)

December isn't exactly a great time to catch astronomical events as it is one of the cloudiest months of the year across the country. So if you can't watch the event on Dec. 21, there are some options to see it online.

If the skies are clear in Toronto, York University's Allan I. Carswell Observatory will host a live online event

In Arizona, where there's a better chance of clear skies, the historic Lowell Observatory will also be hosting a live online event.

And while it's been quite some time since the planets were this close, conjunctions do occur every 20 years this century. But this will be the closest the pair will get for the next 60 years, so try to catch it if you can.

ABOUT THE AUTHOR

Nicole Mortillaro

Senior Reporter, Science

Nicole has an avid interest in all things science. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books.

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