Here's What You Need to Know About the Rare 'Christmas Star' Forming This Month
The rare conjunction between Jupiter and Saturn will land right next to the holiday.
In the early evening this month, Jupiter and Saturn are almost unmissable. The bright pair of gas giants are sitting so close to each other in our night sky that it feels like they could reach out and touch. If you keep paying attention, that will appear to happen. The planets will come together to form a single luminous point of light as a double planet. It will be the first time this has happened since the Middle Ages.
You'll be able to see this gorgeous formation on the night of the winter solstice, December 21. The event is called a great conjunction, but it's also referred to as a "Christmas star." A conjunction, by the way, is the aligning or close pass of two planets from our perspective on Earth. Unlike a supermoon, the "great" of a great conjunction is an earned superlative. It's a rarity, and this one will be the closest they've been since 1226, according to Patrick Hartigan, an astronomer at Rice University.
So, why is it called a "Christmas star"?
Due the event landing near the Christmas holidays, many are referring to the formation as a "Christmas star." Though, Jamie Carter at Forbes says that there's more to the name than simple proximity. He notes that some, including the famous astronomer Johannes Kepler, say that the star of Bethlehem seen by the three wise men in the Christian bible may have been a very rare triple conjunction between Venus, Saturn, and Jupiter.
There's plenty of debate about what the Magi actually saw, however. Some theories about the star of Bethlehem involve a conjunction that wasn't this triple conjunction, while others cite a comet, Uranus, or even a supernova as the cause of the biblical star. No matter what it was, this year's formation and its timing has already evoked that story with the "Christmas star" label being tossed about.
Our perspective on Earth will make this an extraordinary sight, but the planets are still an extraordinarily long way apart in the solar system.
A conjunction between the gas giants takes place about once every 20 years. Though it's not always that visible in the night sky, and it's rarely seen with the planets as close as they will be this year. You'll be able to spot them just after sunset in the southwest sky if you're viewing from the United States. (Though, this conjunction will be visible around the globe as long as you've got clear skies.) They'll be low in the sky and won't be around long before they drop back below the horizon.
Don't miss the amazing sight, because you aren't going to be able to catch one this close again until 2080. Though, that won't be a "Christmas star." That conjunction will take place in May.