Mother nature is celebrating the winter solstice with a rare meeting of the Milky Way’s two biggest planets.
Saturn and Jupiter will experience a conjunction Monday night, getting so close together that from our vantage point, it’ll almost look like they’re touching.
Known as the “Great Conjunction,” the alignment of the two massive planets will appear as a bright star in the sky, just days away from Christmas. That’s why this celestial occurrence has become known as the “Christmas Star.”
And unlike many space events that are only visible to some, this one should be readily visible to anyone in the US with a clear view of the horizon.
However, blink and you might miss it: The farther you are from the equator, the smaller your window to see the conjunction will be.
So what is this cosmic wonder and when is the best time to catch it? All your burning conjunction questions, answered.
What is the Great Conjunction?
Saturn and Jupiter appear to us to align in the sky about once every 20 years. But they rarely get this close. And it’s a sight to behold, since the two planets are the biggest gas bodies in our solar system.
Where in the sky is the Christmas Star?
“You can imagine the solar system to be a racetrack, with each of the planets as a runner in their own lane and the Earth toward the center of the stadium,” said Henry Throop, astronomer in the Planetary Science Division at NASA Headquarters in Washington. “From our vantage point, we’ll be able to be to see Jupiter on the inside lane, approaching Saturn all month and finally overtaking it on December 21.”
When and how can I watch Jupiter and Saturn align?
If you go outside an hour after sunset and look toward the southwestern sky, you may have about an hour to view the two planets. It’ll help to use an app such as Google’s Sky Map, which can be held up to the sky to show where certain planets and stars are located.
The spectacle can be seen with the naked eye, but binoculars or a small telescope may reveal Jupiter’s four large moons orbiting the planet.
Why is it called the Christmas Star?
Jupiter and Saturn are bright, especially during the Great Conjunction, they can be seen from most cities. Remind you of something biblical? Perhaps you’re getting memories of your nativity play? The star of Bethlehem, sometimes called the Christmas Star, guided the wisemen to the birth of Jesus.
And the fact that it’s happening on the winter solstice? Pure coincidence.
“Conjunctions like this could happen on any day of the year, depending on where the planets are in their orbits,” said Throop. “The date of the conjunction is determined by the positions of Jupiter, Saturn, and the Earth in their paths around the Sun, while the date of the solstice is determined by the tilt of Earth’s axis. The solstice is the longest night of the year, so this rare coincidence will give people a great chance to go outside and see the solar system.”
When did this last occur and will it happen again?
The alignment of the two planets hasn’t happened since 1226.
If you do miss it, the two planets will still be relatively close through Christmas — so try the next day. And if you miss it again, well, the next conjunction like this will happen in 60 years.
Why is this special?
The two planets have been rather close in the sky lately, however, “it is fair to say that this conjunction is truly exceptional in that the planets get very close to one another,” Patrick Hartigan, a professor of physics and astronomy at Rice University, wrote in a blog entry on the conjunction.
During this year’s conjunction, “both planets will be visible in the same field of view in most small telescopes, along with some of Jupiter’s and Saturn’s moons,” Hartigan wrote. “In fact, they will be so close it may be a challenge to separate them with the unaided eye for many people.”