Look up at the night sky on Dec. 21 and you may see something special.
The planets of Jupiter and Saturn will appear (weather-permitting) on the winter solstice to be so close from Earth that they may look like one shining star, even though they’ll actually be 450 million miles apart.
The so-called “Great Conjunction” last happened in 1623 but could not be seen from Earth. Before that, the phenomenon previously occurred on March 4, 1226.
2020’s celestial event has been christened by some as the “Christmas Star,” due to its proximity to Christmas Day.
“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 one another,” said Patrick Hartigan, a professor of physics and astronomy at Rice University.
“On the evening of closest approach on Dec 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” Hartigan explained in a statement. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”
“Look for them low in the southwest in the hour after sunset,” NASA recommended on its website. “And on December 21st, the two giant planets will appear just a tenth of a degree apart — that’s about the thickness of a dime held at arm’s length!”
Viewing conditions will improve the closer people are to the equator.
“The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon,” said Rice. “Fortunately, the planets will be bright enough to be viewed in twi-light, which may be the best time for many U.S. viewers to observe the conjunction.”
It also depends on the weather as to how visible the conjunction will be.
Nahum Arav, a professor of physics at Virginia Tech, described the “rare event” as “special because of how bright the planets will be and how close they get to each other in the sky.”
The two planets will be “easily” seen by the naked eye, he said in a statement. “They will be very close to each other, about a fifth of the moon’s diameter. At their closest, some people will need a binocular to separate them.”
The spectacle will next reportedly occur on March 15, 2080.
After that? Well, it’s a bit of a longer wait — until the year 2400.
Support HuffPost
Our 2024 Coverage Needs You
Your Loyalty Means The World To Us
At HuffPost, we believe that everyone needs high-quality journalism, but we understand that not everyone can afford to pay for expensive news subscriptions. That is why we are committed to providing deeply reported, carefully fact-checked news that is freely accessible to everyone.
Whether you come to HuffPost for updates on the 2024 presidential race, hard-hitting investigations into critical issues facing our country today, or trending stories that make you laugh, we appreciate you. The truth is, news costs money to produce, and we are proud that we have never put our stories behind an expensive paywall.
Would you join us to help keep our stories free for all? Your contribution of as little as $2 will go a long way.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
As Americans head to the polls in 2024, the very future of our country is at stake. At HuffPost, we believe that a free press is critical to creating well-informed voters. That's why our journalism is free for everyone, even though other newsrooms retreat behind expensive paywalls.
Our journalists will continue to cover the twists and turns during this historic presidential election. With your help, we'll bring you hard-hitting investigations, well-researched analysis and timely takes you can't find elsewhere. Reporting in this current political climate is a responsibility we do not take lightly, and we thank you for your support.
Contribute as little as $2 to keep our news free for all.
Can't afford to donate? Support HuffPost by creating a free account and log in while you read.
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. Would you consider becoming a regular HuffPost contributor?
Dear HuffPost Reader
Thank you for your past contribution to HuffPost. We are sincerely grateful for readers like you who help us ensure that we can keep our journalism free for everyone.
The stakes are high this year, and our 2024 coverage could use continued support. If circumstances have changed since you last contributed, we hope you’ll consider contributing to HuffPost once more.
Support HuffPostAlready contributed? Log in to hide these messages.