Skip to main content

Planets to appear nearly aligned creating ‘Christmas star’ last widely visible 800 years ago

When something inordinately rare or unexpected happens, it is said “the planets aligned.”

On Dec. 21, the winter solstice, two planets will appear nearly aligned, resulting in an event so uncommon it’s befitting of the saying. At one time, astronomers may have felt it so closely resembled a Christmas miracle — or, perhaps, the star of Bethlehem — that they named the spectacle the “Christmas Star.”

The event is called a conjunction, said Shane Larson, associate director of Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics.

“Conjunctions of Jupiter and Saturn happen every 20 years and most aren’t very close at all. What’s special this year is they’re right, right next to each other,” said Larson. “These two planets have never been this close in the sky for 400 years so no one really knows what it’s going to look like because it hasn’t happened since 1623, in Galileo’s time. That kind of gives you a sense of the rarity of the event. This is not just a once-in-a-lifetime event, this is a once-in-our-history since-we-built-the-telescope event.”

Continue to the full story in the Chicago Tribune, by Katherine Rosenberg-Douglas. Banner image credit: Duluth News Tribune.