What We Know About the Rare "Christmas Star" That Formed in 2020 — and When We'll See It Again
As 2020 came to a close, the solar system decided to grace us with a cosmic Christmas miracle that hadn't been witnessed in nearly 800 years, often referred to as the "Star of Bethlehem" or the "Christmas Star." Unfortunately, we won't see it again in 2021, but on Dec. 21, 2020 (aka the December solstice), Jupiter and Saturn aligned so closely in the night sky that they almost appeared to collide from our vantage point here on Earth, creating a radiant point of light.
"You'd have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky."
"Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to be to one another," said Patrick Hartigan, an astronomer at Rice University, according to Forbes. "You'd have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky."
What Did the Christmas Star Look Like in 2020?
The event, sometimes referred to as The Great Conjunction, occurs roughly every 19 to 20 years, but 2020 was the closest the planets had lined up in the night sky since the Middle Ages. Technically, Saturn was 10 au (astronomical units) from Earth and Jupiter was 5 au away, but they appeared to be less than the diameter of a full moon apart.
The planets were at their closest on Dec. 21, but the Christmas Star was visible from everywhere on Earth for about one hour after sunset in the northern hemisphere for the entire fourth week of December. Those who viewed with a telescope may have also been able to see Jupiter and Saturn's largest moons orbiting them that week.
When Is the Next Christmas Star?
Unfortunately, if you missed the Christmas Star in 2020, the next Great Conjunction this close won't happen until March 15, 2080. For now, you can admire a photo of the rare cosmic event — taken in Colorado — below.