A Heavenly Reunion: The great conjunction of 2020 explained

click to enlarge A Heavenly Reunion: The great conjunction of 2020 explained
Graphic by Alex Brizee/For Inland 360
In space, Jupiter and Saturn are more than 400 million miles away from each other, but from the night sky this month they will appear to get closer and closer together until Monday, when they will appear to touch each other in a sight last seen 400 years ago.

By Alex Brizee

For Inland 360

On and around Monday, Dec. 21, the night sky will be a little more spectacular than normal with the occurrence of what is being called the great conjunction of 2020, a phenomenon some have named the Christmas Star. So what’s happening in the sky? We spoke with Jason Barnes, University of Idaho professor of astronomy and planetary science, by phone to learn about this astronomical event. 

360: Where did the name the Christmas Star come from? 

Barnes: Well, I couldn’t tell you why it’s called that. Presumably, it’s because of the association with the biblical Christmas star and it is happening on Dec. 21.  

360: What actually is this phenomenon that people are talking about? 

Barnes: What’s happening is what’s called a conjunction, which is when two planets get close, as viewed in our sky. 

Jupiter orbits the sun every 10 years, and Saturn orbits the sun every 30 years. So every 20 years or so, Jupiter laps Saturn and, in doing so, they will get close to each other in their orbits.

Sometimes, Jupiter is on the exact opposite side of the sky as Saturn. When they come together, it’s going to be pretty spectacular. 

360: Is this a rare occurrence? When can we expect to see this again? 

Barnes: We do get conjunctions of Jupiter and Saturn, every 20 years they come relatively close to one another. However, Jupiter and Saturn are on different orbital inclinations … because the solar system isn’t strictly a two-dimensional pancake, they don’t always get as close together. 

360: Is there anything special about this occurrence? 

Barnes: What is unusual about this particular conjunction is that Jupiter and Saturn are going to be super close together, only a tenth of a degree. They are so close together that, if you break out a telescope and look, you should be able to see both Saturn and its rings and its moons and Jupiter and its moons, all in one view, which I’ve never seen before, and I’m a professional astronomer. 

The last time they were this close together was 400 years ago, so back in the renaissance, right when Galileo first used the telescope to look at the sky. 

360: What can people expect to see? 

Barnes: You’ll look at the sky and, over the course of the next few days, Jupiter and Saturn will be there and they’ll be the brightest things in the sky. And they’ll get closer and closer to one another. But when you look on (Dec.) 21 it will actually look like a double planet. 

It’s a good test: If you need glasses, you might struggle to split the pair but if your prescription is up to date, you should be able to see the difference between the two and that they are separated by a little bit. 

360: Where should people in the region look to see the conjunction? 

Barnes: About 45 minutes after sunset is a good time to look, and you’ll be looking in the southwestern sky and you do need to look relatively low at the southwestern sky. 

Of course, around here the hardest part is going to be the weather; you have to find a time that is clear. 

360: Can you view the conjunction on a day other than Dec. 21?

Barnes: It’s a slow-motion event, so they’ll get closer and closer together. Any time between Dec. 15 and shortly after Christmas it is still going to be worth looking at, if you get the chance. 

360: Do you need special equipment to see the conjunction? 

Barnes: This is a totally naked-eye event. Jupiter and Saturn are super bright.