Jupiter and Saturn will appear closer in the night sky than they have in 800 years
By: Cody Welch
Tags: Astronomy, Jupiter, Saturn, Space, Great Conjunction

Tonight, on December 21, the two largest planets in our solar system will meet in the evening sky for a rare celestial rendezvous.

Saturn, top, and Jupiter, below, are seen after sunset from Shenandoah National Park, Sunday, Dec. 13, 2020, in Luray, Virginia as they draw closer to each other in the sky, heading towards a “great conjunction” on December 21, where the two giant planets will appear a tenth of a degree apart. Credit: NASA/ Bill Ingalls

Over the past few weeks, Jupiter and Saturn have been inching closer and closer to one another in the night sky. As these two massive gas giants orbit counter-clockwise around the sun, Jupiter has been gradually catching up with its neighbor, until tonight, where the two planets will finally meet.

This event is known as a “great conjunction,” a special moment where Jupiter and Saturn appear closest to each other as Jupiter passes Saturn in its orbit, at least as we see it from the vantage point of Earth.

These conjunctions occur roughly every 20 years. But tonight, the alignment will bring Jupiter and Saturn visibly closer to each other in the night sky than they have been in nearly 800 years, where they will appear just a tenth of a degree apart. That’s about the width of your fingernail held at arm’s length.

The last time these two planets were this close together was actually about 400 years ago during the year 1623. At this time, the astronomer Galileo was alive and active in his field, having just recently discovered 4 of Jupiter’s largest moons (Io, Europa, Ganymede, and Callisto) in 1610 while also unknowingly observing Saturn’s rings, which would not officially be discovered until half a century later.

But at this time, the alignment occurred during the day in the same direction as the sun, making it virtually impossible for Galileo and others to have seen. This means that the last time these two behemoths were this close together in the night sky for humans to see was around 800 years ago during the year 1226, although no one on planet Earth at the time would have had a telescope to observe this incredible event.

That makes this year’s “great conjunction” particularly special. Not only will today be the first time in 800 years since they’ve appeared this close to each other, but it will also be the first time in human history that we will have the knowledge and the technology to observe it so closely, whether it be with a telescope or a simple pair of binoculars.

Jupiter, left, and Saturn, right, are seen after sunset above Jordan Lake during the “great conjunction” where the two planets appear a tenth of a degree apart from one another, Monday, Dec. 21, 2020, near Chapel Hill, North Carolina. Credit: NASA/Bill Ingalls

This is a moment in human history where nearly anyone on planet Earth can look up at the night sky and marvel over these two massive celestial bodies appearing right next to each other in the solar system, with Saturn appearing as close to Jupiter as some of its own moons. And even though these gas giants actually remain hundreds of millions of miles apart in space, from our vantage point here on planet Earth, we get to see them both side by side in all of their grandeur to admire.

2020 has been a rough year, but it’s moments like these that offer a unique opportunity for us all to stop what we’re doing, look up, and gain a little appreciation for our place in the cosmos.