The last few weeks, Jupiter and Saturn have been moving closer and closer in the night sky. On December 21st, their conjunction will be closest. A conjunction is when planets appear to align in the sky. The Great Conjunction is given the word “great” because it’s the two largest planets of Jupiter and Saturn.
Jupiter and Saturn come close to one another at least once every 20 years, approximately, based off their varying revolutions around the sun. Jupiter takes close to 12 years to circle the sun and Saturn, around 29 years. But those more frequent conjunctions are not as close as the conjunction that is happening Monday. Jupiter and Saturn will be about the thickness of a dime apart from each other, if you hold the dime straight up ahead of your view.
It has been quite a while since the last conjunction that will be this close between the two planets. The last similar conjunction of this closeness was July 16, 1623, but it was not visible to the middle latitudes and most of the world’s population. Prior to that, the Great Conjunction of March 5, 1226 had an even closer distance between Jupiter and Saturn and was visible to the majority of the world’s people.
The next Great Conjunction of similar closeness will be March 15, 2080.
To view the Great Conjunction, look low in the southwest horizon during the evening. You will see the planets shining very brightly nearly right on top of each other. The planets have been visible in the night sky for weeks now, but on Monday night, they will be their closest to one another. The forecast for Sunday evening will be cloudy over Iowa, so viewing will not be ideal. However, on Monday December 21st, clear skies are forecast – perfect for taking in the “Christmas Star”.