What’s Up With the Great Conjunction?

We’re not going to lie, the “great conjunction” definitely sounds like some apocalyptic, world ending event that will end Earth as we know it. Maybe another planet is gonna swing by, or some ancient god from another dimension will descend upon us and crush our mortal minds with a simple thought. While such devastation would be a fitting way to end 2020, the great conjunction is actually quite neat, and pretty exciting too. So let’s get to it, what’s up with the great conjunction? 

What’s a Conjunction?

The long astronomical definition of a conjunction is when two objects have the same right ascension or ecliptic longitude relative to Earth. 

Which is a whole lot of nonsense to the average layperson. 

For starters, a conjunction is when two bodies appear close in the sky, even when they’re actually far apart. We effectively see the sky in 2D; without super special equipment, a lot of the “depth” in perspective is lost to us. For example, Orion’s Belt. In that constellation, we have three really bright stars making up well… Orion’s Belt. In case you were wondering, their names are Alnitak, Alnilam, and Mintaka. 

Now from Earth, they look like they’re all lined up on a single plane, stacked up in a neat little row or line. If we were to look from another perspective though, we would find that the stars are actually not lined up at all and sit at varying distances from Earth. It’s kind of like those little sculptures that you can rotate around to make a shadow that looks like something else at the right angle.

Objects like this relative to Earth are ecliptic. They look close to each other relative to Earth because they’re close to each other in the sky. 

Right ascension refers to the position of an object in the sky relative to the Earth’s equator. You can think of it as “longitude for the sky.”

Further Reading: What Is the Difference Between Latitude and Longitude?

Who’s Involved This Time?

This isn’t just any conjunction. It’s the “great conjunction,” which means there’s something special about this one. Something special there is, is the great conjunction refers to the conjunction of Jupiter and Saturn in the sky. You know, the two biggest planets in the solar system. 

These conjunctions happen around every 20 years, which may make 2020’s seem like a relatively mundane occurrence. When we’re observing Jupiter and Saturn in conjunction, they’re typically somewhere between 0.5 and 1.3 degrees from each other in the sky. Which, translating from triangles and geometry, means there’s anywhere between 1 and 2.5 moons in between them in the night sky.

What makes the 2020 conjunction special is that Jupiter and Saturn will actually be less than 0.2 degrees apart in the sky–which has only happened 3 other times since 1226 (not counting 2020, including 1226). Also, it’s at night so you can see it with the naked eye. Most of the time they’re during the day.

What Causes the Great Conjunction?

You may be wondering what drives these conjunctions. They occur every 20 years because that’s when Jupiter appears to overtake Saturn in the night sky. This is, of course, down to perspective–thanks to the solar system not being a flat plane. Plus, the Earth’s equator wouldn’t be lined up with that plane anyway. 

Because these angles are constantly shifting and nothing ever lines up perfectly, we won’t see another conjunction like this until 2080. So uh… Maybe go take a peek outside if you can over the course of the week while you still have the chance. 

Conjunctions are also a language thing. See if you know what we mean here.